chapter Trees & Shrubs - extension.usu.edu · the root system is best. A wide and shallow hole allows good root growth since most roots grow laterally. Rough up the sides of the hole

U ta h S tat e U n i v e r S i t y e x t e n S i o n ~ M a S t e r G a r d e n e r P r o G r a M

14-1

Trees & Shrubs14chapter

INTRODUCTION

Woody plants are perennials with woody stems – including trees, shrubs, many vines and ground covers.

There are three general categories of woody plants: trees typically have one main trunk (although some have multiple trunks) and are taller than 15 feet at maturity; shrubs have multiple stems and grow to less than 15 feet at maturity; and vines which climb, trail or creep and need support. Woody plants are important in landscapes, forests and many other areas. Select, establish and care for the right ones, and they will live for many years. Trees and shrubs are dominant landscape features and provide landscape structure and framework. They benefit neighborhoods and communities through their aesthetic value, softening the environment by providing shade and wind breaks, and increasing property value. They also shelter wildlife and help reduce air pollution.

TREES

Tree Selection

For an excellent online selection guide for trees, go to www.treebrowser.org. This interactive program authored by Dr. Mike Kuhns, Extension Forestry Specialist and Lyle Holmgren, Box Elder County Extension Agent, allows the user to select from more than 240 trees that grow in the State of Utah. Make selections based on size, shape, growing conditions, flowers and many other characteristics. The program also provides landscape uses and pictures of the plant’s leaves, flowers and other important features.

Decide the intended use or plant function in the landscape. No species is perfect, but avoid those that are poorly adapted to the site. Woody plant selection depends on many factors. Consider site characteristics and suitability including soil conditions, salinity, sunlight, exposure, slope, wind and water availability. Consider growth rate, mature size, form, flowering and fruiting habits, longevity, strength, color, insect and disease resistance and water needs. Determine tolerance to cold, heat, pollution, drought, soil pH, salinity and other adverse environmental conditions.

Matching a woody plant to site conditions is a starting point. Consider these factors when evaluating the site for a tree or shrub.

Soil Conditions

Healthy soil provides plants with water, nutrients and adequate aeration and it improves root stability and growth. Landscape soils are challenging because they are often modified by construction and grading practices and are often variable. Utah soils are alkaline (high pH) and low in organic matter. Soil conditions in a landscape may vary greatly from one area to another. It is a good idea to have soil from different areas tested for pH, salinity, texture and nutrient levels. Understanding soil properties helps to avoid possible problems associated with improper plant selection. Water Requirements Some woody plants are more drought-tolerant and can grow with little supplemental water while

by Taun Beddes, Jaydee Gunnell - Horticulture Agents; Larry A. Sagers - Extension Horticulture Specialist;

Heidi Kratsch, Maggie Shao - Former Horticulture Agents;Utah State University Extension


14-2

others require regular irrigation. In most parts of Utah, natural precipitation does not provide enough water for landscape plants. Supplemental irrigation is usually needed, but overwatering weakens and damages tree health. Hydrozoning places plants with similar water needs together in landscapes. Providing separate zones for woody plants and turf helps conserve water and optimizes plant health.

For further information on irrigating woody plants, refer to the following factsheet: http://extension.usu.edu/files/publications/publication/HG-523.pdf.

Temperature Temperature fluctuations and extremes are common in Utah. Before choosing a plant for any location, determine the average coldest temperature expected (hardiness zone), and choose plants accordingly.

The United States Department of Agriculture (USDA) publishes hardiness zone maps. These are included in many gardening books and catalogs or can be found on the internet at: http://www.usna.usda.gov/Hardzone/ushzmap.html. Another useful reference can be found at http://extension.usu.edu/forestry/HomeTown/Select_HardinessZones.htm. This fact sheet shows USDA zones and other temperature information for several areas in Utah. Plants at the extremes of their hardiness range may need to be planted in protected microclimates, behind walls or windbreaks.

Sun Exposure

Microclimates exist in all landscapes. These are different in those that are permanently shaded

Figure 1 - Tree Forms. USU Extension Publication NR-460 “Selecting and Planting Landscape Trees.” Kuhns, M. and Rupp, L. (2000). Available from http://extension.usu.edu/files/publications/publication/NR-460.pdf.

compared to those with high light intensity from reflective surfaces like fences and bricks. High light can scorch sensitive species and cause dehydration and death. Even plants that tolerate full sun conditions suffer if temperatures are excessively high. Choose plants for their tolerance to sun or shade. Pay particular attention during the hottest part of the day. Winter sun is also damaging to broadleaf evergreens. Plant these where they are protected from afternoon sun.

Wind Exposure Wind causes serious damage to Utah landscapes. Cold, dry north winds quickly drop temperatures and freeze exposed plants. This is especially serious in autumn or spring when plants may not be completely hardened off or are breaking dormancy. Daily temperatures that fluctuate by 50°F are common in some open areas. Only the hardiest plants grow in these susceptible sites. Non-native broadleaf evergreens including European cherry laurel (English laurel), photinia and Japanese euonymus are especially susceptible to temperature fluctuation damage. Hot, dry winds during summer months can increase the evaporative demand on plants and cause drought symptoms (scorch within leaf margins and leaf drop). Wind tunnels in urban areas where wind is channeled by buildings or other structures also increase water stress to plants.

Pest and Disease Resistance

Pest and disease resistance is somewhat determined by genetics and environmental

Pyramidal Round Columnar/Weeping Broad Oval Vase Shrubby

Layered


14-3

conditions. Stressed plants are more susceptible to pests. For example, aspens in landscapes are susceptible to many common stresses. Soils are more alkaline, temperatures are warmer and there is less moisture than in their native mountain environment. Stressed aspens are prone to many problems including aspen leaf spot, leaf scorch, Cytospora canker and borers, while ginkgos have few known pests and are pollution tolerant.

Growth Rate

Fast growth rate is a characteristic many desire. Cottonwoods, willows and silver maples are large, fast growing trees that are short-lived, weak-wooded and quickly outgrow their site. Use with caution and plant slower-growing and longer-living trees at the same time.

Rooting Space

The root space plants require is directly related to their canopy size, growth rate and lifespan. When plants grow in areas with insufficient root space they are more susceptibile to pests and diseases and premature death often follows.

Crown Size

Match plant size with the available space. Consider above-ground interferences including power lines, buildings and fences. Strong-wooded trees (such as oaks) can overhang a roof, but plant weak-wooded trees at least one-half of their mature crown width away from buildings.

Form

Plant species and cultivars vary widely in form or crown shape. They are tall and narrow, short and wide, weeping, rounded, conical, upright, vase-shaped or pyramidal. Crown selection is a personal choice but match it to the site and plant function. Use columnar trees in narrow areas while avoiding those with low or weeping branches near driveways or sidewalks. Use those that retain their lower branches for windbreaks or screens.

Purchasing Plants

When purchasing, look for woody plants without insects, diseases, wounds or cultural problems. Look for those with well-spaced and arranged

branches, true to the growth habit. Locally grown plants are often better adapted to local climate conditions.

Types of Planting Stock

Woody plants are purchased in three forms: bare-root, balled-and-burlapped (B & B) or container-grown.

Bare-root: Bare-root plants are field grown and have the soil removed during digging. Their exposed root systems require protection from drying out and from mechanical injury during

handling, storage and planting. Bare-root trees are less expensive. They require special care and are only available in the spring. They must be planted before buds begin growing. Balled-and-Burlapped (B & B): Field grown plants are removed with soil around their roots, and the root ball is tightly secured in burlap. This method is used for larger deciduous or evergreen trees. Because of the costs of labor, they are more expensive than bare-root plants. They can be planted throughout the growing season, although spring or fall planting is preferred. Digging up plants using this method leaves as much as 90% of the roots behind, so the root mass of the tree is greatly reduced. Balled-and-burlapped plants are sometimes placed in containers for convenience. These should still be treated as B & B plants.

Container-Grown: Woody plants grown in a pot or box for at least a season are containerized. They are more expensive than bare-root stock, but generally cost less than

Figures 2 . Types of planting stock - A) Bare-root B) Balled-and-burlapped C) Container

A B C


14-4

balled-and-burlapped plants. The plants are commonly produced in 1- to 25-gallon containers. They can be planted any time that the soil is not frozen, but spring or fall is preferable. Smaller plants cost less and establish more quickly.

The root ball size for B & B and container-grown plants should be proportional to the plant size. One guideline is to allow 12 inches of root ball diameter for each 1 inch of trunk caliper. Some containers have recently potted bare-root or B & B trees placed in pots for convenience. Newly planted containers should be marked with a “non-established” tag.

Tree Installation Soil Preparation

Plant woody stock correctly so it establishes quickly and survives well. Choose a suitable planting location. Construction sites are often littered with waste that interferes with root

growth. Compacted soils inhibit root growth as do chemical, motor oil or gasoline spills. Select well-drained, fertile soils when possible, and use special care when planting trees in clay soils. Dig the planting hole much wider but no deeper than the root ball. A hole at least three times as wide as

the root system is best. A wide and shallow hole allows good root growth since most roots grow laterally. Rough up the sides of the hole with a shovel to increase root penetration. Backfill with the native soil.

Planting

Balled-and-Burlapped

Place the root ball on undisturbed soil in the hole with the root collar or flare just above the surrounding soil. Be careful not to plant it too deep. Never break the root ball but after placing the plant in the hole, remove as much of the wire basket and burlap as possible. This speeds the penetration of roots into the surrounding soil and improves tree survival. Any basket or burlap left underneath the root ball is of little concern, since roots grow laterally. Cut and remove all twine or wire that is wrapped around the trunk. If the soil in the root ball is loose or disturbed, reject the plant if possible.

Fill in around the ball with soil and lightly tamp it to remove air pockets. When backfilling is nearly complete, add water to help settle the soil and eliminate air pockets. After the water soaks into the soil, complete the backfill by adding soil up to the root collar. Do not pack or tamp the soil after watering to avoid ruining the soil structure and inhibiting future root development.

Container-Grown

Plant container-grown trees the same way as balled-and-burlapped trees. Place the root flare and collar slightly above the final soil level. Remove the plant from the container and place the tree in the hole on undisturbed soil. If the root ball in the container is loose, put the pot in the hole and cut away the container and remove it gradually while backfilling to hold the roots and soil in place.

Plants containerized for a year or more often develop roots circling inside the container. These can become girdling roots later in the plant’s life, which can inhibit growth. Remove the container and inspect for any circling roots. Carefully cut circling roots to avoid problems.

Figure 3. Tree installation diagram.


14-5

Bare-root

Bare-root plants need special care during and after planting because their roots are exposed and vulnerable. Plant them as soon as possible or keep the roots moist. Plant them before they leaf out. Dig the hole as described previously. Spread the roots in their natural position and determine the right height for the root flare. Add backfill soil over the roots and gently firm it in place. Straighten the tree, adjust its depth if needed and finish as described for B & B trees.

First Year Care

Fertilizing

Do not fertilize when planting or during the first season. Natural soil fertility usually provides for the plants’ needs without adding more fertilizer. Plants need a season to establish a good root system, and fertilizing promotes leaf and top growth at the expense of root growth.

Pruning

Prune only broken branches or those that are rubbing. DO NOT cut back healthy, live branches to reduce the crown size.

Staking

Most trees do not need staking. Exceptions are large trees that move during strong winds or trees in public areas that need protection from vandalism. If trees must be staked, leave them so they can flex, and do not use wire or other materials that can injure or girdle the plant. Remove the stakes after the first year.

Mulching

The root growth of some trees nearly doubles the first few years after planting if properly mulched. Mulch conserves moisture, reduces weeds, keeps mowers away from trunks, reduces compaction and insulates roots from heat and cold extremes. Cover an area of at least two feet around the trunk with 2 to 3 inches of wood chips, shredded bark or similar materials.

Watering

Water newly planted woody plants when the soil dries out. Irrigation frequency depends on the soil type. Apply enough to soak the soil 18 to 24 inches deep. More new plants die from over-watering than from not getting enough moisture. Trees have deeper and more extensive root systems than turfgrass and other plants. Deep, infrequent watering encourages deeper rooting and makes plants more drought-tolerant.

Woody Plant Maintenance

Irrigation of Trees and Shrubs

The water needs of woody plants depend on species, size, air temperature, humidity, soil type and wind. Roots spread from the trunk to the drip line and beyond and most absorbing roots are in the top 12 to 18 inches of soil. Water the entire root zone to about 2 feet deep. Apply water slowly enough that the soil absorbs it without running off. Applying water too quickly causes puddling, erosion, soil compaction and wastes water. Keep 2 to 4 inches of mulch around a tree to keep the soil moist, discourage weeds and prevent damage from trimmers and mowers.

Soaker hoses or drip emitters allow slow water penetration into the soil. Monitor water infiltration by testing with a probe or metal rod. The probe penetrates wet soil easily but becomes difficult to push when it hits dry soil.

Fall Watering

Before the first hard freeze, water woody plants so the roots have moisture in the fall and winter. Fall watering is most important for evergreens that transpire during warm winter days.

Fertilizing Woody Plants

Need for Fertilization

Planting the right tree in the right place reduces the need for additional soil amendments or fertilization. Healthy plants that show no nutrient deficiences likely need no fertilizer. Additionally,


14-6

plant growth rate can indicate fertilization needs. If growth is less than normal, compare current twig growth with past growth. If there is a significant difference, fertilizing may help. Before fertilizing, determine if other factors such as water stress, root problems, soil compaction, girdling roots, insects or disease problems and construction or winter damage are at fault.

Excess nitrogen fertilizer promotes excessive growth and over time, it weakens plants. This increases insect and disease problems.

Apply fertilizer in late winter or early spring. Do not fertilize from mid summer to early fall as fertilizing then stimulates new growth that will likely winter kill.

Fertilization rates vary with tree and root size. If trees need fertilizer, spread 1 to 2 pounds of actual nitrogen per 1,000 square feet of soil surface under the drip line of the tree. Calculate this as follows:

Surface Area = Radius2 x 3.14 (The radius is the distance from the trunk to the edge of the branch spread or drip line.)

For example, a tree measuring 18 feet from the trunk to the drip line (canopy cover) has an 18-foot radius. The area would equal 18 x 18 x 3.14, or 1,017 square feet. According to the recommendation, apply approximately 1 to 2 pounds of actual nitrogen.

Application

Spread fertilizer uniformly on the soil surface under the tree. If you have turf growing under the tree, make two or three light applications or make holes in the grass to avoid burning the turf.

NOTE: Be careful when applying lawn fertilizers that contain broadleaf herbicides. These products can severely injure or kill trees and shrubs. Make certain that lawn care services do not damage sensitive woody plants by misapplying herbicides.

Pruning

Pruning is the purposeful removal of selected plant parts to get a desired growth response. Avoid the need for excessive pruning by planting the right tree or shrub in the right place so it has room to grow naturally. Pruning does not stop growth but only directs it. Prune to help the tree, and learn to prune carefully and correctly.

The three reasons to prune are: • Health: To remove dead, diseased or dying branches.• Hazard: To remove low, crossing or hazardous branches.• Form: To direct the growth and to shape to a desired form.

Pruning Impacts

Trees adjust internally to the balance of shoot/root. Excessive pruning of woody plants causes these impacts:

• The tree does not form enough food. • It is unable to take up sufficient nitrogen or other nutrients.• It loses valuable food storage tissue. • It uses stored food to survive. • It disrupts connections between shoots and roots. • It stimulates growth in unwanted areas or at unwanted times. • It creates rapid shoot growth at the expense of root growth.

Consider the following when pruning large trees:

• Each woody species has a characteristic shape and form. Pruning may change appearance temporarily but not permanently. Appreciate the natural growth form, and try to enhance it when pruning. • Pruning of any kind places some stress on a plant. Figure 4. Fertilizer Application. Make holes at the drip line of

the tree and place fertilizer there when fertilizing shade trees.


14-7

When to Prune

If possible, prune live branches while dormant. This allows the plant to replace lost branches and foliage during the growing season and close and seal wounds properly. Prune dead branches any time. Bleeding (loss of sap from wounds) can be a problem in birch, maple, elm, grape and walnut trees if they are pruned late in the spring. Avoid this by pruning no later than February to allow freshly exposed wood to harden before the sap flow begins.

Pruning in the summer reduces food production, restricts root development and slows tree growth. Pruning a tree that needs it is better than not pruning at all, but moderate or light summer pruning is preferred for most woody plants. Pruning Tools Use a good pair of hand shears with scissor-action (called by-pass pruners) for pruning twigs and small branches up to 1/2” thick. Use a fine-toothed pruning saw on branches up to 1.5” thick. Remove branches that are smaller than 1.5” with loppers. For higher branches and working from the ground, use a combination lopper/saw on a pole pruner.

Pruning Trees

What to Prune

Small Twigs. Remove the tips back to a viable bud or the next live branch. Do not leave stubs. Stand back and visualize the tree response before making a cut.

Large Branches (over 1 inch in diameter). Good pruning removes as much of the branch as possible without leaving a stub. The recommended method is called natural target pruning. Targets for making cuts are based along lines that the tree forms naturally.

The first target is the branch bark ridge where the branch meets the stem. Every branch has internal tissues that separate it from the trunk. These tissues help in wound closure and self-defense, so protect them during pruning. As the internal tissue forms, the bark is forced upward to form a raised ridge on the trunk that separates the branch from the trunk. This is called the branch bark ridge. The second target is the junction of the lower part

of the branch and the main stem and is called the branch collar. It is the most prominent on younger branches and dead or dying branches. Proper pruning removes the branch so the collar is not injured or removed.

The Three Step Method removes the weight of the limb before the final cut to eliminate the possibility of stripping the bark down the side of the main trunk.

• Undercut to prevent limb breakage. • Cut down and remove the limb. • Trim the branch stub at the collar.

Wound Painting Trees do not heal, they seal. To enhance this natural process, prune carefully to keep the trees vigorous and healthy. Do not use wound dressings such as creosote, tree paint or tar.

Topping

Never top trees for any reason! Topping removes major portions of the tree crown by cutting branches and/or the trunk to stubs. It severely injures trees, leaving them susceptible to pest and decay and can kill them. It drastically reduces their food-producing capacity, destroys natural growth habits and creates large wounds. Topping decreases tree values, and topped trees require

Figure 5. Natural target pruning of broadleaves and conifers. Final cuts should be from A to B.


14-8

continual attention and follow-up treatment for the remainder of their lives.

Pruning Evergreens

Evergreens have leaves or are coniferous with leaves modified into needles or scales that do not drop seasonally. Each type has different pruning requirements.

Prune evergreens to control the size and shape, to remove dead or damaged wood and remove old branches to allow new growth. Evergreens usually need less pruning than deciduous plants.

One common mistake in pruning evergreens is squaring them off with hedge shears. The best way to prune most evergreens is by the “thinning-out” method. Cut back to a lateral side branch or cut a branch completely off at the trunk. The lateral side branch then becomes the new terminal. The thinning-out method of pruning is the least conspicuous. It creates a more open plant with a natural look and does not stimulate excessive new

terminal growth. It allows size reduction without changing the natural plant appearance.

Pruning Conifer Trees and Shrubs

Many conifers including pine, fir and spruce normally grow into broad, pyramid-shaped trees with a single central leader (trunk). Little pruning is required when they are planted in open areas.

Pruning conifers requires special care because they seldom produce new buds or shoots along existing branches or on older wood. Buds for future development are formed primarily on new growth only. Once conifers get too large, it is often too late to start corrective pruning.

It may be possible to narrow trees by cutting branches back to inner side branches that still have live foilage.

Needled evergreens’ growth can be controlled by candling. The candle is the new shoot that grows each spring. Remove one-half of the new terminal growth when fully extended but still soft. This forces side buds to grow and makes fuller plants. (See Figure 10).

Keep side branches from growing out of bounds by removing the terminal bud. This slows outward growth and helps make the plants bushier.

Avoid shearing needled evergreens (except yews). (See Figure 11). This can cause unsightly brown needle tips and negatively impact growth. Avoid cutting too far into the interior of conifers where no green growth is present. Cut branches will not regrow in this situation. Instead, completely remove the branch.

Figure 9. Left tree figure is neglected, center tree figure is correctly pruned and right tree figure is overpruned.Figure 7. Topping trees is very damaging and should

never be done.

Figure 8. Never prune evergreens beyond the green growth.


14-9

Pruning Pines

It is best to plant pine cultivars that are correctly sized for the site and will not need pruning. If pruning is needed, the best time to prune pines is in the spring. Control the height and width of pines by pruning the new soft growth and side laterals in late spring. Pinch off one-half to two-thirds of the candle-like terminal growth by hand before needles unfold. Annual candling reduces the need for heavier pruning in pines.

Pruning Spruces

Begin pruning when growth starts in early spring. Cut leaders back one-half or more of their length, if needed. Cut side branches back to a side shoot or bud.

If a tree develops two leaders, remove the less desirable one in early spring. Trees with multiple leaders are weaker and less attractive.Occasionally trees may have their leader destroyed. If this happens, tie one top branch to a vertical stake until it becomes dominant. The tree may look slightly irregular, but it can be carefully trimmed so the tree develops a normal shape.

Pruning Junipers

The best time to prune junipers is before they start growing in the spring so new growth will cover any errors and be more attractive. Dwarf, slow-growing types require little pruning; faster growing, spreading forms may need extensive pruning to retain a compact, symmetrical form. Upright juniper forms often require much more pruning to maintain a dense symmetrical shape. Prune using the thinning-out method to retain the natural habit of growth. Prune ragged branches in early spring and clip new growth in June to control size and shape. Cut out branches completely if they become overcrowded.

Common evergreens and their pruning requirements are as follows:

Arborvitae (Thuja) Clip ragged branches in early spring to shape the plant; prune new growth in June to control size and shape.

Figure 10. Pinch out new growth of needled evergreens.Figure 12. Pruning pines.

Figure 13 . Pruning spruces.Figure 11. Shearing results in excess terminal twigs and an unnatural look.


14-10

False Cypress (Chamaecyparis) Prune new growth to control size and shape. These plants are only semi-hardy in our area.

Fir (Abies) Pinch back new shoots (candles) about half way to promote new side growth.

Yew (Taxus) Prune ragged branches in early spring and clip new growth in June to control size and shape.

Pruning Shrubs

Prune shrubs by the thinning-out or the renewal method. (See Figure 15 and 16). When thinning out, cut a branch or twig off the main trunk to a side branch or to ground level. This opens up the plant without stimulating excessive new growth. Carefully thin out the plant without changing the plant’s natural appearance or growth habit. Use hand pruners, not hedge shears, to maintain a given height and shape by removing the older, taller stems each season.

Renewal Pruning

Renewal pruning gradually removes the oldest branches at the ground level from an overgrown shrub leaving younger, more vigorous branches. This controls shrub size while maintaining a healthy, natural look. This method is also used to rejuvenate old overgrown shrubs. Do this over a 3 year period. Help new shoots develop into strong branches by cutting them back to various lengths using the thinning method. The ideal time to prune most woody plants is during the dormant season before new growth starts. Prune spring blooming shrubs after they flower.

Deciduous shrubs shed their leaves each fall. Prune them to control their size, shape and flowering. Remove dead, diseased or damaged wood when it appears. Shrubs allowed to grow to their natural size and shape need less pruning than hedges that are trimmed to specific designated sizes and shapes.

New shoots grow the way the buds point. Keep shrubs growing to their natural shape by thinning branches to buds facing the direction where growth is needed. Before cutting branches or stems, imagine how the plant will look when new shoots appear, and prune the plant to direct the growth.

When pruning to a bud, make a slanted cut about even with the top of the bud. When removing an entire branch, cut back to the stem. When cutting out dead wood, cut just above live wood at the bud.

Topped Shrubs

One common mistake in pruning shrubs is to cut them all back to the same height. This should only be done when creating hedges. Topped shrubs develop excessive sprouts at the cut areas.

These shade the base of the shrub so the shrubs end up with leggy stems and bushy growth on the top. This makes them very unsightly.

Pruning Broad-Leafed Evergreens

Broad-leaved evergreens which go into winter with flower buds already formed are pruned immediately after flowering. Prune those that

Figure 15. Pruned using the shearing method.

Figure 16. Pruned using the thinning method.

Figure 14. Pruning junipers.


14-11

produce flowers on new wood during the dormant period in late winter or early spring. Avoid fall pruning as it may stimulate growth and reduce plant hardiness.

Prune broad-leaved evergreens as formal hedges as necessary to shape them. When pruning branches to promote new growth or shape the plant, cut back to a bud or green shoot. Without a bud or shoot on the plant, there is no new growth.

On plants with several stems that may need pruning, cut old, leggy stems to the ground to promote new growth from the base of the plant. Do not cut back all old stems in one year, but use a renewal pruning system where one-third of the old stems are removed annually. Remove flowers as they fade. Prune dead or diseased wood at any time. Trees that have already grown too wide can be narrowed down by cutting branches back to an inner bud.

Common broad-leaved evergreens and their pruning requirements are as follows:

Azalea, Rhododendron and Magnolia: Prune branches after flowering to promote new growth; cut back leggy stems. Do not over-prune these plants and do not prune in late summer.

Boxwood (Buxus): Cut branches and stems to keep plants compact. It tolerates shearing and can be pruned to topiaries or formal hedges.

Euonymus (Euonymus): Use as hedges or prune to natural free-form shape. Judicious pruning helps control powdery mildew.

Holly (Ilex): Prune lightly to moderately to control size and shape but don’t over-prune. Prune at Christmas and use the branches for decorations.

Laurel (Prunus laurocerasus): Cut back old stems and branches to control size and shape. Hand clip; to avoid leaf damage, do not shear.

Oregon Grape (Mahonia spp.): Cut back the stems to keep them from becoming leggy.

Photinia (Photinia): Prune to control shape and size.

Privet (Ligustrum): Glossy privets are evergreen and are grown in the St. George area. Prune to control shape and size.

Viburnum (Viburnum): Some species of viburnum are evergreen. Prune to control size and shape. Avoid excessive pruning.

Figure 17. Topped shrubs.

Figure 18. Pruning cuts. There are three kinds of cuts made on woody plants. Thinning cuts direct the growth to a specific direction. Removal cuts take the stem out at ground level. Heading cuts stimulate several buds to grow beneath the cuts. They are primarily used when pruning formal hedges.


14-12

Pruning Flowering Shrubs

The flowering characteristics of shrubs determines pruning technique. To encourage flowers or fruit, observe where the flowers are produced on a shrub.

Prune shrubs that flower on the mid-portions of their stems by removing 1/3 of the oldest stems near the base of the plant annually. Make thinning cuts on the remaining stems as necessary.

Prune plants that flower at the terminal tips by removing a few of the older canes and spindly stems at or near ground level. Head back vigorous stems to force branching and new tips where desired, and thin others as needed.

Plants that flower on mid portions of stems: • Barberry (Berberis spp.) • Beauty bush (Kolkwitzia amabilis) • Cotoneaster spp. • Forsythia spp. • Holly (Ilex spp.) • Honeysuckle (Lonicera spp.) • Mock orange (Philadelphus spp.) • Spiraea spp.

Plants that flower on terminal tips: • Dogwoods (Cornus spp.) • Lilac (Syringa spp.) • Magnolia spp., shrubby • Oregon Grape (Mahonia spp.) • Photinia spp. • Privet (Ligustrum spp.) • Serviceberry (Amelanchier spp.) • Viburnum spp.

Spring-Flowering Shrubs

Blooms on spring flowering shrubs form on growth produced the previous year. Pruning these shrubs in the winter months removes flower buds that would produce blooms the following spring. Prune spring flowering shrubs after they finish blooming.

Common spring-flowering shrubs and their pruning requirements are as follows:

Almond, flowering (Prunus glandulosa) — Prune branches to shape the plant.

Beauty Bush (Kolkwitzia amabilis) — Prune old wood as necessary to promote replacement growth.

Broom (Cytisus spp.) — Prune to control size and shape.

Cotoneaster (Cotoneaster spp.) — Prune branches to control size and shape. Many spreading cotoneasters should be pruned very sparingly.

Currant (Ribes spp.) — Remove 3-year-old wood to promote new growth and encourage berries.

Chokecherry (Prunus virginiana) — Remove old wood as needed to increase flowering and fruit.

Dogwood (Cornus sericea) — Prune out 3-year-old stems to promote new growth.

Dogwood (Cornus spp.) — Remove old wood by renewal pruning.

Elderberry (Sambucus spp.) — Prune to shape. Older stems die back naturally.

Firethorn (Pyracantha spp.) — Prune to control size and shape. Severe pruning reduces the number of berries.

Flowering Quince (Chaenomeles spp.) — Prune to control size and shape. Severe pruning reduces the number of flowers.

Forsythia (Forsythia spp.) — Cut old stems to the ground as necessary to promote new growth.

Honeysuckle bush (Lonicera tatarica) — Prune to the ground to control spreading growth and to retain compact appearance.

Lilac (Syringa spp.) — Remove suckers, old flowers and stems older than 3 years unless training to a tree form.

Magnolia (Magnolia spp.) — Remove seed pods and prune branches to shape plants.

Mock Orange (Philadelphus spp.) — Prune 3-year-old wood to promote new growth.

Ninebark (Physocarpus spp.) — Prune crowded stems to thin and promote new growth.


14-13

Oregon Grape (Mahonia aquifolium) — Prune out the old damaged stems and keep the plants shaped correctly.

Potentilla (Potentilla spp.) — Shear after flowering to keep plants blooming.

Rose of Sharon (Hibiscus syriacus) — This requires little pruning in most cases.

Serviceberry (Amelanchier spp.) — With flowering training, do renewal pruning.

Spirea (Spiraea spp.) — Some common early flowering types are Bridal Wreath and Vanhoutte. Remove three-year-old wood and prune branches to shape the plant.

Viburnum (Viburnum spp.) — Many kinds of viburnum are grown for flowers and fruit. Some of the more common kinds are Viburnum burkwoodi, V. carlesi, V. fragrans, V. opulus, V. macrocephalum, V. sieboldi, and V. tomentosum mariesi. Renewal prune to control their shape and height.

Weigela (Weigela spp.) — Prune old branches and thin new growth as necessary to prevent crowding.

Witch Hazel (Hamamelis mollis) — Remove old wood to control size and promote new growth.

Summer-Flowering Shrubs

Summer-flowering shrubs bloom on wood produced the same season. Prune during the dormant season before growth begins. Many are sheared to ground level each year. Common summer-flowering shrubs and their pruning requirements are as follows:

Bluebeard (Caryopteris clandonensis) — Cut stems to near ground level annually to promote new growth.

Butterfly bush (Buddleia davidii) — Cut stems to near ground level annually to promote new growth.

Honeysuckle (Lonicera fragrantissima) — Prune old stems and branches as necessary to control size and promote new growth.

Hydrangea (Hydrangea paniculata and H. arborescens) — Prune back to a few buds to promote new growth and cut out crowded stems as necessary.

Roses (Rosa spp.) — Prune varieties that bloom once, after they finish blooming. Deadhead other ornamental varieties by cutting back to a five leaflet.

Snowberry (Symphoricarpos spp.) — Prune stems back to a few buds. Cut out crowded stems and branches as necessary.

Spirea (Spiraea spp.) — Summer-flowering spirea cultivars include from S.x bumalda, S. japonica and S. nipponica. Cut out crowded stems as necessary and cut other stems back to a few buds. Remove seed pods when they form.

Sumac (Rhus spp.) — Common types are staghorn and smooth sumac. These need little pruning except to prevent them from spreading and to remove dead wood. Prune the stems to the ground to promote new growth. Sumac can be trained to a single trunk tree by allowing one stem to grow.

Pruning Hedges

Hedges require more pruning to maintain their shape than free-form shrubs. After planting, cut hedges back to six to eight inches. This forces new shoots near the ground to develop into thick, bushy growth. When 8 to 12 inches of growth are formed, cut this back by 50%. This causes formation of dense branches and foliage. Prune as needed during the growing season.

Two hedge forms are common: formal and informal. Prune formal hedges to a predetermined size and shape one or more times each growing season. Prune informal hedges (often a row of shrubs planted closely together, but allowed to grow normally) annually to thin out the oldest wood and maintain the desired height and width.

Pruning a Formal Hedge

Trim the top of the hedge to a slightly rounded or tapered shape. This allows sunlight to reach the lower branches. If the top is as wide as or


14-14

wider than the base, the lower portion is shaded and produces thin, weak growth. Tall hedges require more attention to maintain proper shape and taper.

Keep hedges vigorous by thinning out 1/3 to 1/4 of the oldest branches annually. Prune branches in the spring before growth starts.

Time to Prune

Hedged deciduous shrubs can be pruned almost anytime. Shear slow-growing hedges that require one annual pruning after they complete their season’s growth in early to mid-June. Trim fast-growing hedges two or more times per year: in early June, mid-July and in mid-September if needed.

Rejuvenating Old Hedges

Restore overgrown, neglected deciduous hedges over a three year period. Cut back older branches to a few inches above the ground before new growth starts in the spring. This is in addition to regular shearing. Another way is to cut back the top and sides of the hedge eight or more inches inside of the desired height and width in early spring. Follow by shearing the new growth for a thick, twiggy effect.

Selecting Shrubs

Introduction

Urban and suburban landscapes present special challenges. Shrubs and all other plants must

withstand high solar radiation, low relative humidity, drying winds and limited rainfall. All these increase water demands on plants. Shrubs growing in Utah must adapt to local conditions that are different than their native environment.

Many shrub species grow well in the state. They soften architectural structures and provide effective screens for privacy. Their various forms, colors and textures also add variety to the landscape. The following charts contain information about shrub selection and care and lists of shrubs that are commonly planted or could be planted in Utah. Use it as a reference, always considering the varied and unique conditions in many areas of the state.

Shrubs and Site Selection

Woody plants are more permanent than herbaceous annuals and perennials and are a greater investment of time and money. One way to protect that investment is to plant shrubs in the right place the first time. Survey the landscape and assess the different factors that affect the long-term survivability of the plants. It is much easier to choose the right shrub for the conditions than to try to modify those conditions for the shrub. Factors to take into account include: shrub size and form, soil conditions, available moisture, temperature, sun exposure, wind exposure and intended use or purpose of the plants.

Shrub Size/Form

The most important, and often overlooked, attribute of shrubs is their mature size (height and width). Place appropriately sized plants so they do not block views or damage the property near a house or building, particularly beneath windows or awnings. For example, Rhus typhina (staghorn sumac) tolerates a wide variety of urban conditions, but its size potential (15 to 25 feet) makes it a poor choice for planting near the house.

Rhus aromatica ‘Gro-Lo’ (Gro-Lo fragrant sumac) is a good substitute because its mature height is only two to four feet.

Be wary of planting shrubs near streets or sidewalks because they can block walkways. One example is Cornus sericea (red twig dogwood). This shrub can reach 12 feet in width, and, if used

Figure 20 . Good Hedge Form..

Figure 21. Poor Hedge Form.


14-15

in narrow sites, must be pruned excessively, which affects the shrub’s health and ornamental quality. Check local ordinances before planting shrubs in parking strips, as there may be restrictions for public areas.


14-16

Selected Shrubs for Utah LandscapesTaun Beddes - Extension AgentUtah State University Extension

Pink Abelia 4 x 4 (6)7 to 9 No Medium Hybrid between A. x grandiflora and A. schumannii that features purple-pink flowers. It blooms from May or June until frost, but can have iron chlorosis in high pH soils. If grown on the Wasatch Front, protection is required. A. x grandiflora is more cold hardy than ‘Edward Goucher.’

Size Hardiness

(H x W in feet)

Zone

Utah Century Plant

1 x 2 (4)5 to 10 Yes Low to very low Utah century plant has gained in popularity in Utah, especially in waterwise landscapes. It is still relatively unavailable. But other cold hardy agaves are becoming more common.

Size Hardiness(H x W in

feet)Zone

Saskatoon Serviceberry

10 x 10 4 to 8 Yes Medium Native to Canada, the Northern Great Plains and the Western US, it is available from local garden centers. Cultivar ‘Regent’ is more compact and refined than the species.

Common Name

Utah Native

Water Use Requirements

Comments and Description

Amelanchier (Serviceberry or Shadblow): Genus of shrubs and small trees native to Asia, Europe and North America. Fruit from many species is edible and is commonly eaten raw and used for syrups and jellies. Another beneficial characteristic of the species includes excellent fall color ranging from brilliant orange to orange-red.

Species Common Name

Utah Native





A. alnifolia

Abelia (Abelia): Abelias are commonly used in warmer areas of the US and grown primarily for their ornamental flowers. They prefer acidic soil which limits their use in much of Utah.

A. x 'Edward Goucher’

Common Name

Utah Native

Species

A. utahensis

Size (H x W in

feet)

Hardiness Zone

Agave (Agave): Agaves, also known as century plants, are ubiquitous in the Southwest. However, recently it has been found that some species are more cold tolerant than previously thought. They add unique ornamental qualities to the landscape and are becoming more common in much of the state.

Species


14-17

Selected Shrubs for Utah Landscapes (cont’d)


feet)Zone

Common Name

Utah Native



Amelanchier (Serviceberry or Shadblow) (cont'd)

Species

Apple Serviceberry

20 x 20 4 to 8 No Medium This natural hybrid of A. arborea and A. leavis, available in nurseries. Sometimes trained as a tree.

Utah Serviceberry

10 x 10 4 to 8 Yes Low Native to the Western US, this species is more drought tolerant than other Amelanchiers.


feet)Zone

Manzanita 1-2 x 8-10 2 to 6 Yes Low This hybrid is very similar in appearance to A. patula and is much easier to propagate and establish. It has evergreen foliage and pink-white flowers in late spring. It is a great replacement for shade tolerant groundcovers in a waterwise landscape.

Bearberry 0.5 x 4 2 to 6 Yes Medium Excellent groundcover for sandy, infertile soils. It does well in partial shade, but can be slow and difficult to establish.



A. patula x nevadensis

Species Common Name

Utah Native

A. x grandiflora

A. utahensis

Arctostaphylos (Bearberry): Also called Kinnikinick, these evergreen shrubs are native to the west. They grow from the oak-maple scrubland forests to alpine regions and produce berries used for wildlife. Some species are slowly becoming more available.

A. uva-ursi


14-18



feet)Zone

Red Chokeberry

6 -10 x 3-5 4 to 9 No Medium Late summer fruit that turns red. The cultivar ‘Brilliantissima’ has glossier green leaves and improved fall color.

Black Chokeberry

3-5 x 3 4 to 9 No Medium Late summer fruit that matures to a dark purple or almost black color. The cultivar ‘elata’ is better than the species.

Size(H x W in

feet)Black

Sagebrush1-2 x 1-2 3 to 6 Yes Low Similar to common sagebrush, but is smaller

and greener and more adapted to landscape use. Evergreen with interest year round.

Big Sagebrush 1-12 x 5-8 3 to 6 Yes Low This shrub is commonly used in native landscapes, but is not particularly attractive as a specimen shrub. Many subspecies exist and A. t. ssp. vaseyana and wyomingensis are better for the landscape.

Size(H x W in

feet)Fourwing Saltbush

4 x 6 2 to 10 Yes Very low Tough plant that survives in all conditions in Utah with low maintenance. Used in naturalized plantings and as screens.

A. tridentata

Aronia (Chokeberry): This genus includes two species, both native to the Eastern US. They have brilliant red fall color and fruit that is sometimes consumed for antioxidant properties. This species can also become leggy with age and renewal pruning is sometimes necessary.

A. melanocarpa

Species Common Name

Hardiness Zone

Utah Native



Species Common Name

Hardiness Zone

Utah Native

Atriplex (Saltbrush): Saltbrushes are tolerant of salty soil, used as browse by wildlife and are very drought tolerant. In the landscape, they are primarily used in areas with saline soil and where supplemental water is unavailable.

A. canescens

A. nova



Artemisia (Sagebrush): Artemisia is a large genus of native plants that contains both herbaceous and woody plants with grey-green foliage. Many exhibit a unique fragrance.

Species Common Name

Utah Native



A. arbutifolia


14-19


Size(H x W in

feet)

Species Common Name

Hardiness Zone

Utah Native

Atriplex (Saltbrush) (cont'd)



Shadscale 3 x 3 3 to 6 Yes Low to very low This species has attractive blue foliage that turns peach in the winter.

Size(H x W in

feet)Centennial

Broom2 x 6 8 to 10 No Medium to low Groundcover plant native to desert areas of

the Southwest. The cultivar ‘Centennial’ produces ornamental flowers and copious amounts of seed. ‘Thompson’ is similar in appearance and seedless.

Size(H x W in

feet)William Penn

Barberry4 x 4 (5)6 to 8 No Medium An evergreen barberry, commonly planted in

areas where foot traffic is not desired. B. julianae (Juliane Barberry) has a similar look.

Mentor Barberry

10 x 10 5 to 8 No Medium A hybrid between B. julianae and B. thunbergii, its appearance is more similar to B. thunbergii featuring red leaves in the growing season. It remains evergreen in warmer areas. This older species is not as commonly planted as B. thunbergii cultivars.

B. mentorensis

A. confertifolia

Baccharis (Broom or Groundsel Bush): This genus is native to the Americas and is common in areas with poor soil conditions.

Common Name

Hardiness Zone

Utah Native



Berberis (Barberry): Genus native to all continents except Australia and Antarctica. Species have thorny branches that make them amenable for use in hedgerows. Deciduous species offer excellent fall color. Many evergreen types but many are not hardy in Utah, except a few that will grow in warmer areas of the Wasatch Front, Moab and Utah’s Dixie. Evergreen species’ leaves turn plum-purple or red in the winter and back to green in the summer; a nice landscape feature. Evergreen species may also require winter protection from afternoon sun and wind to prevent leaf scorch.

Species Common Name

Hardiness Zone

Utah Native



B. x gladwynensis ‘William Penn’

B. x ‘Centennial’

Species


14-20


Size(H x W in

feet)

Common Name

Hardiness Zone

Utah Native



Berberis (Barberry) (cont'd)

Species

Japanese Barberry

Variety Dependent

4 to 7 No Medium Although red-leaved forms are most commonly planted, green-leaved varieties such as ‘Kobold’ are an excellent substitute for the harder-to-grow Buxus (boxwood) species especially in colder areas. Several yellow-leaved varieties are becoming more available, but may suffer from summer leaf scorch in our dry climate. ‘Aurea’ is a popular yellow leaved variety. Consider cultivars such as ‘Crimson Pygmy’ and ‘Bagatelle’ where space is limited. ‘Rose Glow’ is another excellent cultivar that reaches 5 feet high and wide.

Size(H x W in

feet)Alternate-leaf Butterfly bush

8 x 8 5 to 9 No Low Tolerates summer heat well. Flowers are borne on one-year-old wood; therefore, prune after bloom. May be difficult to find.

Butterfly bush 10 x 10 5 to 9 No Low Tolerates summer heat well. The shrub becomes leggy if not properly pruned. Flowers borne on current season’s growth. Attracts butterflies and other pollinators. There are many cultivars available that vary in flower color, eventual size and leaf variegation.

B. thunbergii

Buddleia (Butterfly bush): Butterfly bush has been used in the landscape for many years. A main benefit of the plant is that it blooms in mid-summer when most other shrubs are not. Its flowers are also very fragrant with a scent somewhat reminiscent of lilac blossoms.

B. davidii

Species Common Name

Hardiness Zone

Utah Native



B. alternifolia


14-21


Size(H x W in

feet)Korean

Boxwood3-6 x 3-6 4 to 8 No Medium Korean boxwood is better for Northern Utah.

Many cultivars are available such as ‘Winter Gem’, ‘Green Beauty’, ‘Green Mountain’ and ‘Julia Jane’.

English or Common Boxwood

6 x 6 (5)6 to 8 No Medium This survives in warmer Wasatch Front areas and may require winter protection from the sun and wind. Variegated forms are available. Used as a container plant with proper winter protection.

Size(H x W in

feet)C. arborescens 15 x 15 2 to 7 No Low Not common but available. Two weeping

forms, ‘Pendula’ and ‘Walker’, are grafted on a standard and are more commonly planted. 'Walker' has ferny foliage and 'Pendula' has typical foliage texture.

Size(H x W in

feet)C. martinii 4 x 8 3 to 6 Yes Medium Broad-leaved evergreen shrub with vanilla

like aroma. May scorch in winter sun and availability is limited.

Utah Mountain Lilac


Species Common Name Hardiness Zone

Utah Native




Buxus (Boxwood): Various boxwood species and cultivars are common in Utah. They are all evergreen, very conducive to hedging and are often pruned into formalized shapes. Boxwoods may suffer from winter sun and wind scorch; protection may be necessary.

Ceanothus (Mountain Lilac): Members of this genus are native to the American West, primarily California. Many species are evergreen and feature lilac-like spring flowers and fragrance. These plants are not closely related to true lilacs (Syringa ).


Utah Native


B. sempervirens

Caragana (Peashrub): Peashrubs are among the most cold hardy shrubs available. They also have ornamental, yellow spring flowers. However, many species have thorns.


B. microphylla var. koreana

Species Common Name

Hardiness Zone

Utah Native


14-22


Size(H x W in

feet)

C. ledifolius 10 x 10 3 to 8 Yes Very low Attractive evergreen shrub with red stems. Tolerates hedging. Also used as a specimen plant. C. intricatus is a smaller, similar species.

C. montanus 5 x 5 3 to 6 Yes Low Deciduous cousin of C. ledifolius . Has good form and attractive fruit.

Size(H x W in

feet)C. millefolium 4 x 4 4 to 10 Yes Low to very low This shrub has unique fern-like leaves,

reddish bark and small white flowers in mid-late summer. Pruned to the ground to maintain compact appearance.

Size(H x W in

feet)

C. speciosa 8 x 6 4 to 8 No Medium Plant is available but less popular. Chaenomeles japonica (Japanese flowering quince) more common but may not be adapted to some areas.

Common flowering quince

Fernbush


Utah Native



Chaenomeles (Flowering Quince): This genus is not extremely popular, but is present in the landscape, especially at older homes. It is mainly planted for its pink-to-red spring flowers which are considered its main ornamental feature.

Curl Leaf Mountain Mahogany


Utah Native



Alderleaf Mountain Mahogany

Chamaebatiaria (Fernbush): This genus is part of the rose family, contains only one species and is native to the Intermountain West.


Utah Native



Cercocarpus (Mountain Mahogany): This is another genus with members native to western areas of the North American continent. The genus contains both deciduous and evergreen species that are browsed by wildlife.


14-23


Size(H x W in

feet)C. linearis 15-30 x 15-

307 to 9 Yes Low Commonly used in Washington County for

showy pink spring flowers. May not be completely cold hardy along the Wasatch Front but may survive with protection.

C. x Chitalpa tashkentensis

15 x 15 6 to 10 No Low Hybrid between Catalpa bignonoides and C. linearis. Has ornamental pink flowers and is considered sterile.

Size(H x W in

feet)C. nauseosus 4-6 x 4-6 3 to 6 Yes Very low Bright yellow to gold bloom in later summer

contrasts with grey-green foliage. Used in naturalistic settings or mass plantings. Prune to keep compact shape. Once established, little irrigation is needed. Size variation is common with this species and it reseeds readily.

Size(H x W in

feet)6 x 6 2 to 7 No Medium to high Commonly planted. Light green leaves with

creamy margins that turn burgundy to purple in fall.


Utah Native



Desert Willow


Utah Native




Utah Native



Chilopsis (Desert Olive): Genus in the begonia family with similar flowers to catalpa and trumpet vine.

C. alba ‘Argenteo marginata’

Variegated Dogwood

Cornus (Dogwood): The most commonly planted dogwood species in Utah are shrub forms. They are well adapted in wetter areas but are moderately drought tolerant once established. Dogwood shrubs are generally fast growing and can become slightly unkempt over time. They can be pruned to the ground and allowed to re-grow. Care should also be taken to provide appropriate spacing when planted.

Chitalpa

Chrysothamnus (Rabbitbrush): This shrub group is native to the Intermountain West and commonly confused with sagebrush. It features grey-green foliage and brilliant yellow flowers. Has a pungent aroma.

Rubber Rabbitbrush


14-24


Size(H x W in

feet)


Utah Native



Cornus (Dogwood) (cont'd)

Variety dependent

2 to 7 Yes Medium to high Native to riparian (wet) areas of the Western US. Very common in the landscape. ‘Baileyi’ grows to 12 feet high and wide, ‘Isanti’ grows to six feet and ‘Kelseyi’ grow to 2 feet high and wide. Both ‘Ivory Halo’ and ‘Silver and Gold’ are common variegated forms. ‘Flaviramea’ is a yellow stem variety.

Size(H x W in

feet)12 x 12 4 to 8 No Medium Shrub with branches that have a very

twisted or contorted growth habit. Use as a specimen plant. It is slow growing and usually fruitless.

15 x 15 4 to 8 No Low to medium Less available in nurseries. Interesting plant with brilliant purple leaves that fade to green with summer heat. Produces edible fruit.


feet)Zone

15 x 15 4 to 8 No Low Green, purple and yellow leaf forms. Prune to 12" in early spring for more intense summer color.

Species Comments and Description

C. coggygria Common Smokebush or

Smoketree

Common Name Utah Native


Purple Giant Filbert

Cotinus (Smokebush or Smoketree): Two species exist, one native to Europe and the other the US. Both have striking ornamental features including showy, plume-like blossoms and brilliant fall flowers. Genus is closely related to the sumacs (Rhus).

Species Common Name

C. avellana ‘Contorta’ Contorted Filbert

C. maxima ‘Purpurea’

C. sericea (stolonifera) Red Osier Dogwood

Corylus (Filbert or Hazelnut): Tree species are far more common in this genus. However, a few smaller forms are planted as shrubs.

Hardiness Zone

Utah Native




14-25



feet)Zone

Species Comments and DescriptionCommon Name Utah Native


Cotinus (Smokebush or Smoketree) (cont'd)

20 x 20 4 to 8 No Low Somewhat less common. Can be trained into a small tree. Tolerant of alkaline soil. Currently, only green-leaved varieties exist.


feet)Zone

10 x 10 4 to 7 No Medium Deciduous species commonly planted as a hedge for attractive fall color.

1 x 10 4 to 6 No Medium Commonly used as a groundcover. It is somewhat shade tolerant. It has a tendency to collect trash in public areas.

3 x 5 4 to 7 No Medium Common evergreen species is often used as a hedge and for soil retention on hillsides. When pruned, it sometimes gets a twiggy or stemmy appearance.

1 x 6 5 to 8 No Medium Evergreen in warmer areas of Utah, this species is similar in appearance to C. divaricatus. ‘Coral Beauty’ is a common cultivar.


C. adpressus Creeping Cotoneaster

C. apiculatus Cranberry Cotoneaster

C. dammeri Bearberry Cotoneaster

C. acutifolius Peking Cotoneaster

C. obovatus American Smoketree

Cotoneaster (Cotoneaster): Multiple species are common in the landscape where they are used as a hedge/barrier plant and sometimes used as groundcovers. Both deciduous and evergreen species exist. Most deciduous species have orange to red fall foliage. All cotoneasters have pungent, white spring flowers that are attractive to pollinators. Another ornamental feature is orange to red fruit that persists in the winter.

Species Common Name Utah Native



14-26



feet)Zone


Cotoneaster (Cotoneaster) (cont'd)



6 x 8 4 to 7 No Medium Used interchangeably with other hedge plants and is adaptable to various landscape conditions. Orange to red fall color lasts for 4-6 weeks.

3 x 5 (4)5 to 7 No Medium Useful as a groundcover with branching structure that has a herringbone appearance. ‘Tom Thumb’ is a common cultivar.

10 x 10 3 to 7 No Medium Similar to Peking Cotoneaster but superior in form and function. Red fall color lasts 4 - 6 weeks. It is not as available as other cotoneasters.


feet)Zone

4 x 4 (5)6 to 8 No Medium More common in warmer Utah areas. It is extremely showy when in bloom. Common cultivars include ‘Allgold’, ‘Burkwoodii’, ‘Lena’. C. x praecox is also commonly available. Genista lydia is closely related and is only hardy to zone six.




C. divaricatus Spreading Cotoneaster

Cytisus (Scotch Broom): Evergreen shrub commonly grown for its early spring flowers that vary in color from yellow to pink. It is only hardy to zone 6. Many species of this genus are potentially invasive.

C. scoparius Scotch Broom

C. horizontalis Rockspray Cotoneaster

C. lucidus Hedge Cotoneaster


14-27


Size(H x W in

feet)3 x 3 4 to 8 No Medium The most durable daphne species, it holds

its leaves until late fall or early winter. Has light pink or white flowers. ‘Carol Mackie’ (variegated) and ‘Somerset’ are two common cultivars.

4 x 4 5 to 8 No Medium More common in the east and larger than other daphnes. It is a parent of Burkwood daphne.

2 x 2 4 to 7 No Medium Bright pink flowers with a groundcover-like growth habit. It is more sensitive to poorly drained soil.


feet)Zone

4 x 4 (5)6 to 10 No Low to very low Plant is less available in Northern Utah nurseries. Plants grown from high elevation seed sources may improve cold hardiness.

D. wheeleri Desert Spoon


Utah Native



Dasylirion (Desert Spoon): Genus related to yucca and agave commonly grown in the desert Southwest. Some species are hardy along the Wasatch Front in protected sites such as warm south walls and other areas that are sunny but protected. These plants may offer a very interesting texture.

Species Common Name Comments and Description

Daphne caucasica Caucasian Daphne

Daphne cneorum Rose Daphne

Utah Native


Daphne x burkwoodii Burkwood Daphne

Daphne (Daphne): Refined plants commonly used for their fragrant flowers. Grow daphnes in well-drained soil and provide winter protection from the sun and wind.


14-28



feet)Zone

2-4 x 2-4 3 to 6 Yes Very low This shrub has green bark and jointed stems. Used in waterwise landscapes. Slow growing but uncommon in nurseries.

Size(H x W in

feet)6 x 6 4 to 8 No Medium One of the most common shrubs in Northern

Utah due to its brilliant red fall color. Regular fertilization is needed. Tolerates pruning. The cultivar ‘Rudy Haag’ only grows to 4 feet high and wide.

Variety dependent

(4)5 to 8 No Medium Grows as mounding groundcover or climbing vine with many variegated forms. They include ‘Emerald Gaiety’, ‘Emerald and Gold’, ‘Harlequin’, ‘Moonshadow’ and ‘Canondale’. Cold hardiness varies.

Wintercreeper Euonymus

E. alatus ‘Compactus’ Dwarf Burning Bush




Ephedra: This genus is an ancient relative to conifers native to the Intermountain West and Asia.

Common Name Hardiness Zone

Utah Native



E. fortunei

E. viridis Green Mormon Tea

Species

Euonymus (Euonymus): The Euonymus genus contains both deciduous and evergreen species commonly planted in Utah. Euonymus shrubs are adaptable to Utah soils but are not considered drought tolerant.

Variety dependent

(6)7 to 9 No Medium May experience winter damage in northern climates and better suited to warmer areas of Utah. Multiple variegated forms, dwarf and columnar forms available. ‘Chollipo’, hardy to zone 5 or 6, is considered more cold hardy and sun tolerant than other cultivars.

6 x 6 (5)6 to 9 No Medium A green leaf species similar in habit and form to Japanese Euonymus, but supposedly more cold hardy.

Size(H x W in

feet)5 x 5 3 to 10 Yes Low to very low Excellent ornamental shrub for natural

settings. White blooms from June to August and attractive feathery seed heads. Looks unkempt if not pruned.


Utah Native



E. japonica Japanese Euonymus

E. x kiautschovicus ‘Manhattan’

Manhattan Euonymus

Fallugia: This genus includes one ornamental species that has attractive flowers and seed heads. Native to rocky slopes from the Southwestern US to Mexico.

F. paradoxa Apache Plume


14-29


Size(H x W in

feet)5 x 5 3 to 10 Yes Low to very low Excellent ornamental shrub for natural

settings. White blooms from June to August and attractive feathery seed heads. Looks unkempt if not pruned.

Size(H x W in

feet)Variety

dependent8 to 10 No Medium Commonly grown as an ornamental in

Washington County. It has showy flowers and edible fruit. Fruit flavor better in areas with cooler summers.

Size(H x W in

feet)10 x 10 5 to 9 Yes Low Shears well to form a hedge or screen or

used as a small specimen tree. Bright green leaves and the new wood is a dark brown-black that fades to cream-white. Shrub produces showy yellow flowers in the spring and blue-black berries in late summer.


F. sellowiana Pineapple Guava


Utah Native




Utah Native



F. neomexicana New Mexico Privet or Desert

Olive

Forestiera (New Mexico Privet): Closely related to common privet, Forestiera naturally grows in riparian areas. A single species is native to Utah while others exist throughout the Southwest and Northern Mexico.


Fallugia: This genus includes one ornamental species that has attractive flowers and seed heads. Native to rocky slopes from the Southwestern US to Mexico.


Utah Native

Feijoa (Pineapple Guava): This genus contains one species native to South America. It is grown in warmer areas of the US and produces a flavorful, edible fruit somewhat similar in taste to the better known guava.

F. paradoxa Apache Plume


14-30


Size(H x W in

feet)10 x 12 8 to 10 No Very low Common in Washington County. This

species works well in waterwise landscapes.

Size(H x W in

feet)15 x 15 (4)5 to 8 No Medium Adaptable to a wide variety of soil conditions

and is becoming common in the nursery. It flowers in late summer and has very attractive bark and fruit. Substitute Crape Myrtle in the North.

Size(H x W in

feet)

12 x 8 5 to 9 No Low to medium Widely planted because of its long bloom season. Flower color ranges from pure white to shades of red, pink and purple. It also grows as a single trunked tree. Many cultivars.

Rose-of-Sharon


Utah Native



Heptacodium (Seven-son Flower): This genus, native to China, is very rare or extinct in the wild. It is an excellent plant for Utah.


Utah Native




Utah Native


H. syriacus

Hibiscus (Hibiscus): Genus of over 200 species mostly native to tropical and subtropical areas. One shrub hibiscus is winter hardy along the Wasatch Front.

H. miconoides Seven-son Flower


F. splendens Ocotillo

Fouquieria (Ocotillo): This genus is native to Northern Mexico and the Southwestern US. They are very unique in their look and add a dramatic statement to the landscape. They have fragrant flowers but also many thorns.


14-31


Size(H x W in

feet)4 x 4 4 to 9 No Medium to high White flowers blooming in late spring or

early summer. Grow in part-shade. Prune to the ground in early spring. Flowers can be dried. “Annabelle’ and ‘Grandiflora’ are common cultivars.

3-6 x 3-6 6 to 9 No Medium to high Most common hydrangeas in the US but difficult in Utah. It is grown for its blue and pink flowers. In alkaline soils, flower color is pink and in acidic soils, color is blue. White-colored cultivars do not change with variations in pH. Flowers on one-year-old wood and flower buds are often damaged in winter.

10 x 10 3 to 8 No Medium to high Better adapted to northern Utah. This underutilized species has white flowers that also benefit from protection.

5 x 5 5 to 8 No Medium to high Adaptability to Utah. Flower color begins as white and eventually fades to pink.


Utah Native



H. macrophylla Bigleaf Hydrangea

H. paniculata PeeGee Hydrangea

H. quercifolia Oak-leaf Hydrangea

H. arborescens Smooth Hydrangea

Hydrangea (Hydrangea): Hydrangea species are native to Europe, Asia and North America. They prefer a slightly acidic, well-drained soil and often perform better in protected microclimates.

Size(H x W in

feet)

3 x 4 (5)6 to 8 No Medium Dieback is common in harsh winters. Cut to the ground in the spring. Re-grows vigorously with 3” wide golden yellow flowers borne in June.


Utah Native



Hypericum (St. John’s Wort): This genus features both herbaceous and woody plants. Yellow blooms appear in late spring or summer. More common in cool, moist climates. Many species are available, but few are suitable for use in Utah’s landscape.

H. ‘Hidcote’ St. John’s Wort


14-32


Size(H x W in

feet)10 x 10 (4)5 to 7 No Medium Meserve hollies are actually an entire group

of hybridized plants. Leaves are dark blue-green, often with spines on the margins. Protect from winter winds and sun. Cultivars include ‘Blueboy’, ‘Bluegirl’, ‘Blue Prince’ and ‘Blue Princess’.

Size(H x W in

feet)Dependent on cultivar

3 to 9 No Low ‘Pfitzer’ is an older cultivars and grows to 5-10’ tall. Foliage is sage green. Other cultivars include ‘Hetzii’ and ‘Seagreen’.

Dependent on cultivar

2 to 5(6) Yes Low Prefers colder climates and varies in size from small shrub to groundcover. The form is more prostrate and very dense.

1-4 with variable spread

3 to 9 No Low Prostrate species that develop purple color in winter. Many cultivars available including ‘Blue Rug’ and ‘Blue Chip’.

2 x 10-12 4 to 9 No Low Groundcover ‘Nana’ will drape over structures. ‘Greenmound’ is lower growing.


3 to 7 No Low A widely planted common cultivar is ‘Broadmoor'. Variety tamariscifolia, often called Tam grows 1-3’ high and 10-15' wide.


4 to 7 No Low Many cultivars available. ‘Blue Carpet’ grows 1’ high by 4-5’ wide and has blue-green foliage. ‘Blue Star’ has silver-blue foliage and grows 3’ x 3’. Sometimes grafted onto a standard.

I. x meserveae Meserve Hybrid Hollies


Utah Native



J. sabina Savin Juniper

J. squamata Single-Seed Juniper

J. communis Common Juniper

J. horizontalis Creeping Juniper

J. procumbens Japanese Garden Juniper

J. chinensis Chinese Juniper

Juniperus (Juniper): Junipers are excellent drought tolerant shrubs, trees or ground covers. They tolerate a wide range of soil conditions, but die when overwatered. The younger leaves are awl-like (sharp), while the mature foliage becomes scale-like. Foliage color ranges from green to blue.


Utah Native


Ilex (Holly): Extensively hybridized evergreen and deciduous shrubs that are native to the Northern Hemisphere . Many are not cold hardy in northern Utah and require acidic soil. A male and female plant are needed to produce ornamental berries.



14-33


Size(H x W in

feet)7 x 7 8 to 10 No Medium Ornamental gray-green foliage and flowers.

It also tolerates heavy shearing. Many cultivars are available.

Size(H x W in

feet)10 x 10 4 to 7 No Medium Used as a hedge and has white flowers in

late spring to summer. Flowers are often not seen due to hedging. More desirable species are available.

7 x 7 7 to 9 No Medium Evergreen shrub grown in Washington County.

10 x 10 5 to 8 No Medium Yellow foliage in the spring. This look can be maintained throughout the growing season with light shearing.

Variety dependent

4 to 8 No Medium Common cultivars include ‘Cheyenne’ that grows to 10’ high and wide and ‘Lodense’ that reaches 4’ high and wide.


Utah Native



Utah Native



L. frutescens Texas Sage

L. japonicum ‘Texanum’ Texas Privet

L. x vicaryi Golden Vicary Privet

L. vulgare European Privet or Common Privet

L. amurense Amur Privet

Ligustrum (Privet): Fast growing shrubs that grow well in urban environments and undesirable soils. Most species tolerate pruning and function well as hedges or screens. Some species have an invasive nature.

Leucophyllum (Texas Ranger): Genus native to the Southwestern US and Mexico and contains drought tolerant species.



14-34


Size(H x W in

feet)6 x 6 4 to 7 Yes Medium Native to Western US and Canada. It

tolerates some pruning and attracts hummingbirds and wildlife to its yellow flowers and black fruit.

10 x 10 4 to 7 No Medium Cultivars are common including ‘Claveyi’ and ‘Miniglobe’. These tolerate severe pruning and are used as formal hedges. Use as a replacement for boxwood in colder climates.

Size(H x W in

feet)6 x 6 (4)5 to 8 No Medium Broad-leafed evergreen is shade tolerant.

Foliage turns reddish-purple in the winter. Yellow spring flowers with dusty-blue berries in late summer. ‘Compacta’ is a cultivar 3 to 4 feet high and wide.

6 x 6 4 to 6 Yes Very low This species has attractive dusty-blue foliage.

1 1/2 x 3 4 to 8 Yes Medium Used as a drought adapted shaded groundcover. Features yellow spring flowers and reddish-purple winter foliage. Tolerates sun better than other Mahonia species.

M. fremontii


Utah Native



Utah Holly

M. repens Creeping Oregon Grape

Species Common Name

M. aquifolium Oregon Grape

L. xylosteum European Fly Honeysuckle

Mahonia (Oregon Grape Holly):This genus is closely related to the barberries (Barberis ) and species are sometimes included within it. All species are considered evergreen.

Hardiness Zone

Utah Native



L. involucrata Twinberry

Lonicera (Honeysuckle): The Honeysuckle genus includes both vine and shrub species, many of which have fragrant flowers and berries utilized by wildlife. Unfortunately, many have become invasive in different parts of the world, including both Tatarian and European fly honeysuckle.


14-35


Size(H x W in

feet)

4 x 6 (6)7 to 10 No Medium to high This species performs best in protected microclimates. Bamboo-like foliage, tolerates pruning. Common cultivars include ‘Gulf Stream’, 'Moonbay’ and ‘Harbor Dwarf’.

Size(H x W in

feet)10 x 10 8 to 10 No Medium to low Commonly grown in Washington County. It

has long flower season, white to pink flowers.

Size(H x W in

feet)6 x 6 4 to 8 No Medium Species is common and has been

hybridized. Common cultivars are ‘Minnesota Snowflake’. ‘Miniature Snowflake’ and ‘Natchez’. ‘Natchez’ is considered to be superior.

3 x 3 4 to 7 Yes Medium to low A native species with promising landscape potential. Availability is limited.

Sweet Mock Orange

N. domestica Nadina or Heavenly Bamboo


Utah Native



Common Name Hardiness Zone

Utah Native


Nandina (Heavenly Bamboo): Native to Asia, this species is not a true bamboo, but is a member of the barberry family.

Species

Philadelphus (Mock orange): Mock oranges are native to Europe, Asia and North America. Most species, many of which have been extensively hybridized, feature fragrant, white flowers that are similar in scent to citrus flowers or jasmine. Renewal pruning may be necessary to maintain form.

P. microphyllus Little Leaf Mock Orange


P. virginalis

N. oleander Oleander


Nerium (Oleander): Native to the Mediterranean and Middle East, this species is the only member of its genus.


Utah Native


Documents

chapter Trees & Shrubs - extension.usu.edu · the root system is best. A wide and shallow hole allows good root growth since most roots grow laterally. Rough up the sides of the hole