2

Plants for a Livable Delaware is a campaign to identify and promote superior plants that thrive without becoming invasive.

A Livable Delaware plant must• Possess adaptable characteristics to landscape

situations (i.e. drought resistant, tolerant of poor soils, etc.)

• Pose no potential threat as an invasive plant• Have no serious disease or insect problems• Be hardy to Delaware

Livable Delaware Plants are identified at some garden centers, public gardensand natural areas in Delaware. They provide safe and desirable alternatives to invasive plants.

An invasive plant can quickly overwhelm and displace existing native plants byreducing the availability of light, water, nutrients and space. They have few, if any,natural controls to keep them in check. Ecologists now rank invasions by exoticplants, animals, and pathogens second only to habitat loss as a major threat tolocal biodiversity.

Invasive plants may be introduced intentionally or by accident. Plants havebeen introduced to control erosion, provide wildlife food and habitat, or for orna-mental value in gardens. A small but destructive group of ornamentals has escapedthe garden and caused damage to forests, fields, wetlands, and waterways.Accidental introductions occur when people and goods travel worldwide. Packingmaterials can harbor seeds or plant parts. Japanese stilt grass, now a widelyescaped groundcover in woodland edges, is a prime example.

3

Invasive plants can be divided into two categories—(1) those plants that wereintroduced but are no longer sold (for example, multiflora rose, autumn olive andoriental bittersweet) and (2) ornamental plants still grown and sold. The formerare so aggressive that while few people (if any) are still planting them, these plantsare abundant in natural or abandoned areas. The challenge with this category is todevelop and implement effective controls.

This brochure focuses on invasive plants still sold and requested. The goal is toeducate the gardening public about invasive plants and suggest desirable alterna-tives for home and commercial landscape use. The worst invasive plants producelarge numbers of seed dispersed by wind, water, wildlife or people. Plants thatspread aggressively by runners or underground stems can also be invasive, creatingproblems when planted close to natural areas.

A serious invader sold in a state or county where it seems harmless might even-tually find its way—through catalog or Internet sales, informal seed swaps, or evenas a cutting in Aunt Mary’s purse—to regions where it will cause harm. The goalof this brochure is to promote primarily native alternatives to potentially invasiveornamental species allowing each individual gardener to choose desirable and safeplants for their gardens. Delaware natives, designated by symbol N on the accom-panying lists, provide some of the best alternatives, not only because of theiradaptability to the local conditions, but also because they provide opportunity tosave and expand the regional beauty and refinement that is our natural heritage.

A team of scientists, naturalists and nursery industry professionals conductedassessments on many plants and developed an Official Delaware Invasive PlantList based on scientifically valid criteria. The following are descriptions of some ofthe worst invasive plants still sold in Delaware and the conditions under whichthey are most likely to cause problems. A list of suggested alternatives is includedfor each problem plant. The alternatives are suggested based on their ability togrow in similar environments and perform the same function in the garden, butmay not possess identical ornamental characteristics. Once fully informed, eachgardener can make his or her own decision about which plants to grow.

The University of Delaware is committed to assuring equal opportunity to all persons and does not discriminate onthe basis of race, color, gender, religion, ancestry, national origin, sexual orientation, veteran status, age, or disabilityin its education programs, activities, admissions, or employment practices as required by Title IX of the EducationAmendments of 1972, Title VI of the Civil Rights Act of 1964, the Rehabilitation Act of 1973, the American withDisabilities Act, and other applicable statutes. Inquiries concerning these statues and information regarding campusaccessibility should be referred to the Affirmative Action Office, 305 Hullihen Hall, (302) 831-2835 (voice), (302)831-4552 (TDD).

Problem

Norway maple (Acer platanoides)originated in Europe and Western Asia.It is a medium- to large-sized (to 50’)shade tree with a broad crown that castsa very dense shade. Norway maple canbe distinguished from other similarmaples by the milky white sap that oozesfrom leaf stalks when cut. It is one ofthe last trees to hold yellow leaves in thefall. Norway maples have been plantedextensively because they tolerate toughlandscape sites, especially in urban envi-ronments. Because they cast a denseshade, release chemicals that are toxic toother species, and have a shallow compet-itive root system that results in very drysoil, few plants other than Norway mapleseedlings grow below them. The result ishomogenous stands of Norway maple,especially in urban parks, where prolifi-cally produced seeds are carried fromstreet tree plantings by wind andstormwater runoff.

4

Norway mapleAcer platanoides

SolutionAlternative shade trees include:

Red maple (Acer rubrum) – 60’, denserounded shade tree with excellent red fallcolor and tolerance to both wet and dryconditions (N)

European hornbeam (Carpinus betulus‘Fastigiata’) – pyramidal to oval; 40-60’tree with late, yellow fall color and toler-ance of wet and dry conditions

Katsuratree (Cercidiphyllumjaponicum) – 40-60’ with pyramidal towide-spreading habit; leaves emerge red-dish purple, change to bluish green insummer, and yellow in fall; may requirewater during drought periods

Kentucky coffee tree (Gymnocladusdioicus) – 60-75’ with a narrow ovalcrown that tolerates dry soil and urbanconditions, short-lived fall color but greatbold winter structure

Sweet gum ( Liquidambar styraciflua)– 60’ pyramidal tree; purple, orange andyellow fall color on the same tree and tol-erance of urban conditions (gumballs canbe messy) (N)

Black gum (Nyssa sylvatica) – 30-50’irregularly rounded tree with green glossysummer foliage and brilliant red foliage in fall; tolerates wet, dry and urban conditions (N)

Swamp white oak (Quercus bicolor) –50-60’ rounded tree with yellow-bronzefall color and excellent drought toleranceas well as tolerance to wet and urban con-ditions (N)

Shingle oak (Quercus imbricaria) –30-45’ conical tree; leaves unfold red inspring with lustrous dark green summercolor and yellow-brown fall color; toler-ates wet, dry and urban conditions (N)

(N) = native to Delaware

5Black gum leaves

Black gum Red maple

Kentucky coffee tree

fleecy flowers later in spring; tolerant ofurban conditions, sun, and shade (N)

Flowering dogwood (Cornus florida)– 20-35’ tall, horizontally branched tree;white bracts covering tree in early spring;not tolerant of urban conditions (N)

Hawthorn (Crataegus viridis ‘WinterKing’) – 20-35’ tall pyramidal tree withwhite flowers in spring and red fruit per-sisting throughout winter (N)

Carolina silverbell (Halesiatetraptera) – 30-40’ tall tree with white,bell-shaped flowers in early spring; toler-ates dry soil (N)

Crabapple (Malus ‘Donald Wyman’)– 20’ tall spreading tree with early springflowers that start white and fade to pink;red fall fruit, effective into the winter;tolerant of urban conditions and thiscultivar is resistant to typical crabapplediseases

Sourwood (Oxydendrum arboreum) –25-30’ tall pyramidal tree; summer flow-ers, brilliant red fall color; fruit capsulesand interesting winter structure; requireswell-drained, acid soil (N)

Okame cherry (Prunus x incamp‘Okame’) – 20-30’ tall, broadly colum-nar when young and spreading to arounded outline with age; carmine-pinkflowers in March-April

Japanese Stewartia (Stewartia pseudo-camellia) – 20-40’ tall pyramidal tree;large white flowers in July; sinuous exfo-liating bark; basically problem free butrequires good moist soil conditions

6

ProblemBradford pear Pyrus calleryana ‘Bradford’

Solution

Bradford pear or Callery pear(Pyrus calleryana ‘Bradford’ and othercultivars) – is a small- to medium-sized(30-50’) flowering tree that originated inChina. It has a rapid growth rate andshort life span with branches that splitunder wind and snow. Newer cultivarsdeveloped to correct the splitting prob-lem produce seed prolifically throughcross-pollination with ‘Bradford.’ BecauseBradford pear was planted so extensivelyand the seed is spread by birds, it threat-ens many open and natural areas. Thetree has a lollipop habit, is covered withwhite flowers in early spring and hasgood burgundy fall color.

Alternative small to mediumspring flowering trees:

Serviceberry (Amelanchier xgrandiflora) – 15-25’ tall with very earlywhite flowers covering the tree, attractivefruit and orange fall color; singlestemmed cultivars are available (N)

Fringetree (Chionanthus virginicus) –25’ tall tree with spreading habit; white,

7

Serviceberry

Sourwood

Fringetree

Crabapple

Solution

Bayberry (Myrica pensylvanica) - 5-12’tall upright rounded shrub, can suckerand form colonies; leathery leaves aresemi-evergreen and aromatic; great formassing or borders; tolerates sun to par-tial shade, dry to wet soil and salt (N)

Eastern ninebark (Physocarpus opuli-folius ‘Diablo’) - 5-9’ tall spreading,upright shrub, interesting exfoliatingbark; white flat-topped flower clusters inlate spring; highly adaptable to urbanconditions; Diablo cultivar has attractivedeep burgundy colored leaves (N)

Fragrant sumac (Rhus aromatica‘Gro-low’) – 2’ high, wide-spreadingshrub with yellow flowers in very earlyspring and orangish red fall color; tolerates shade or sun and dry conditions;can be rejuvenated by mowing to ground

Spirea (Spiraea japonica‘Atrosanguinea’) - 3-4’ high spreadingshrub; deep rose, red leaves and flowers;tough, adaptable to urban conditions,prefers full sun

Spirea (Spiraea ‘Flaming Mound’) 2’by 2’ mounded shrub with flaming redfoliage, red flower buds turning yellow,dark pink flowers; tough, adaptable tourban conditions, prefers full sun

American Cranberrybush Vibernum(Viburnum trilobum) - 8-12’ roundedshrub, showy white flowers in May toearly June, producing red berries; yellowto reddish-purple fall color; prefers fullsun to part shade; adaptable

Highbush blueberry (Vacciniumcorymbosum) – 6-12’ upright shrub; whiteurn-shaped flowers, blue fruit and brilliant red fall color; tolerates wet soilconditions (N)

8

Japanese barberry (Berberis thun-bergii) was introduced as an ornamentalin the late 1800s. It forms dense stands in a variety of habitats including closedcanopy forests, open woodlands, wetlandsand open fields. Barberry spreads vegeta-tively and by seed. This highly shade-tolerant shrub displaces natives whereverit becomes established. Barberry cultivars are grown for their red leaf colorand/or compact habit.

Alternatives to barberry include:

Slender deutzia (Deutzia gracilis‘Nikko’) – 2-4’ tall by 3-4’ wide, lowmounded shrub with bright green sum-mer leaf color and pure white flowers thatcover the plant for 2 weeks in spring

Helleri holly (Ilex crenata ‘Helleri’) –1 1/2’ by 2’ mounded shrub with smallevergreen leaves

Virginia sweetspire (Itea virginica) -3-5’ shrub with arching branches formingcolonies; white fragrant flowers in June-July and lasting garnet red fall color;prefers full sun to part shade; tolerateswet and dry conditions once established(N)

ProblemJapanese barberryBerberis thunbergii

9

Fragrant sumac

Eastern ninebark

Spirea

Virginia sweetspire

flies, especially monarchs; prefers drysandy soils (N)

Joe pye weed (Eupatorium fistulosum)- 5’-7’ tall with huge rounded purpleflowers in August-September; prefers fullsun to partial shade, moist, wet soil;attracts butterflies (N)

Woody plants:

Sweetshrub (Calycanthus floridus) – 6-9’ broadly rounded shrub; burgundyflowers with fruity fragrance in May (cultivar ‘Athens’ has yellow flowers) andlingering into July; yellow fall color isvariable with cultivars; trouble-free,adaptable shrub

Sweet pepperbush (Clethra alnifolia) -4-8’ tall with smaller cultivars; whitedelightfully fragrant flowers in July-August borne in upright spikes (pink cul-tivars are available); fall color is pale yel-low to rich golden as the season progress-es; tolerates wet, shade, sun and salt (N)

Bottlebrush buckeye (Aesculus parvi-flora) - 8-12’ in height; wide-spreading,suckering shrub with ascending pictur-esque candelabra branching; tall,grandiose white flowers borne above thefoliage in June-July; excellent massed or asa specimen; tolerates both sun and partialshade

Bush-honeysuckle (Diervillasessilifolia) - 3-5’ high suckering shrub;sulfur yellow flowers are borne from Junethrough August; flowers on new wood soit should be pruned back in spring justlike butterfly bush; extremely tough plant(N)

10

Solution

ProblemButterfly bushBuddleia davidii

Butterfly bush (Buddleia davidii),originally from China, has been grown asan ornamental since 1900 and hasescaped from gardens into disturbed areassuch as roadsides, open fields and water-ways. The shrub is often rangy andunkempt. In the garden, many seedlingscan be found at the base of an existingbutterfly bush. Flowers are a nectarsource for butterflies, but the plant doesnot provide food for butterfly larvae.

Alternatives for butterfly bushinclude:

Perennials:

Blue giant hyssop (Agastache foenicu-lum) - 2-3’ tall with blue flowers in Julythrough September; prefers full sun anddry conditions; many cultivars are avail-able in a wide array of flower colors; allare butterfly magnets

Butterfly milkweed (Asclepiastuberosa) - 1-3’ tall with tight clusters ofshowy, waxy, yellow to deep orange flow-ers borne on downy stems through thesummer; particularly attractive to butter-

11

Wild hydrangea (Hydrangeaarborescens) - 3-5’ tall rounded shrub;flowers are white and borne in 4-6" flatclusters in June; ‘Anabelle’ has extremelylarge flowers; cut to ground in late fall orearly spring for best flowering; will getmultiple reblooms if pruned after flower-ing; prefers partial shade but does well infull sun with sufficient moisture (N)

Crape myrtle (Lagerstroemia indica) –15’ tall in southern Delaware and can betreated as yearly cutback in northernDelaware; flower colors from white topink, purple and deep red; bloomingthroughout summer; thrives in hot, sunnyclimates

Elderberry (Sambucus canadensis) - 5-12’ tall multi-stemmed, suckering shrub,6-10" wide cream to white flowers thatcover plant in June-July, large droopingclusters of deep purple berries relished by48 species of birds; tolerates a wide rangeof conditions; good for naturalizing (N)

Bush-honeysuckle

Butterfly milkweed

Sweet pepperbush

Joe pye weed

12

Winterberry holly (Ilex verticillata‘Winter Red’) – 6-10’ in height, similarspread; prefers moist, acid soil; sun topart shade; attractive yellow to red fallcolor; excellent winter berry appeal (N)

Virginia sweetspire (Itea virginica) –3-5’ shrub with arching branches formingcolonies; white fragrant flowers and last-ing garnet red fall color; tolerates wet anddry conditions (N)

Smooth sumac (Rhus glabra) – 9-15’suckering shrub; great for large areas buttoo aggressive for a small garden; orange-red-purple fall color with persistent scarletfruit; tolerates dry conditions (N)

Highbush blueberry (Vacciniumcorymbosum) – 6-12’ upright shrub; whiteurn-shaped flowers, blue fruit and bril-liant red fall color; tolerates wet soil con-ditions; has all the attributes of burningbush plus white flowers and edible fruit!(N)

Maple leaf viburnum (Viburnum acer-ifolium) – 4-6’ low branching shrub thatforms thickets; pink, rose to purple fallcolor; tolerates dry soil and shade (N)

Arrowwood viburnum (Viburnumdentatum) – 6-8’ dense, multi-stemmedshrub; good rosy pink to red fall color(N)

Winterthur viburnum (Viburnumnudum ‘Winterthur’) – 6’ shrub with asuckering rounded habit; white flowersand excellent purple fall color that persiststhroughout the fall; tolerates wet soil (N)

ProblemWinged burningbush Euonymus alatus

Solution

Winged burning bush (Euonymusalatus) originated in Asia and Japan and isplanted for its brilliant red fall color, darkgreen summer leaves and winged stems.It has been used as a medium-sized (5-10’) shrub in the landscape. It spreadsprimarily by bird dispersal of seeds so itsimpact can be far-reaching. There areportions of woodlands in Delaware withan entirely red autumn understory due tothe dominance of burning bush.

Alternative moderate sizedshrubs include:

Red and black chokeberry (Aroniaarbutifolia ‘Brilliantissima’ and Aroniamelonocarpa) – 6-10’ upright shrub withwhite flowers and red or black berries;naturalizing habit; brilliant red fall color;tolerates wet, dry and urban conditions (N)

Red twig dogwood (Cornus sericea) –7 to 9 foot multi-stemmed shrub with redstems in winter; tolerates wet conditions(N)

Dwarf fothergilla (Fothergillagardenii) – 3-6’ rounded shrub with whitefragrant flowers and great yellow, orangeand scarlet fall color

13

Winterberry holly

Red twig dogwood Dwarf fothergila flower

Smooth Sumac

Dwarf fothergilla leaves

14

Red or black chokeberry (Aroniaarbutifolia ‘Brilliantissima’ and Aroniamelanocarpa) – 6-10’ upright shrub withwhite flowers and red or black berries;upright, naturalizing habit; brilliant redfall color; tolerates wet, dry and urbanconditions (N)

Forsythia (Forsythia x intermedia) – 8-10’ arching shrub; more attractive withnaturalistic habit but can be pruned intoa hedge; grown for yellow flowers in earlyspring; tolerates tough conditions

Inkberry (Ilex glabra) - upright ever-green shrub growing 6-8’ tall; good cleandark green leaf; makes a good foundation,hedge or mass; quite shade tolerant andgrows in sun with ample moisture (N)

Bayberry (Myrica pensylvanica) - 5-12’tall upright rounded shrub, can suckerand form colonies; leathery leaves aresemi-evergreen and aromatic; great formassing or borders; tolerates sun to par-tial shade, dry to wet soil and salt (N)

Blackhaw viburnum (Viburnumprunifolium) - 12-18’ tall, considered amulti-stemmed shrub to small tree; handsome clean foliage in summer withpinkish red to bronze fall color; useful formassing and shrub border as well as specimen planting; sun or shade and tolerates dry soil (N)

Eastern ninebark (Physocarpus opuli-folius ‘Diablo’) - 5-9’ tall spreading,upright shrub, interesting exfoliatingbark; white flat-topped flower clusters inlate spring; highly adaptable to difficulturban conditions; Diablo cultivar hasattractive deep burgundy colored leaves(N)

Solution

ProblemPrivetLigustrum species

Privet, including border, European,Chinese, and Japanese (Ligustrum obtusifolium, L. vulgare, L. sinense, L. japonicum) were introduced to theUnited States as garden plants through the18th, 19th and 20th centuries and arewidely used as hedges. White flowers andblack berries are debatably ornamental.Berries are dispersed by birds and otherwildlife. Chemicals in the leaves protectthe plant from insects. Border privet isthe most commonly documented escapeein Delaware, but all four species haveinvasive potential and have spread intofloodplains, forests, wetlands and fieldsthroughout the eastern U. S. It formsdense thickets and out-competes nativevegetation.

Alternatives for privet include:

Glossy abelia (Abelia x grandifolia) -3-6’ rounded, dense spreading multi-stemmed shrub with arching branches;fine textured, lustrous dark green to purple-bronze, semi-evergreen foliage;white-pink persistent flowers late springuntil frost

15

Spirea (Spiraea nipponica‘Snowmound’) - 3-5’ high spreading shrub;dark blue-green leaves; erect multiple stemswith arching branches result in roundtopped fountain-like form; profuse whitespring flowers; tough, adaptable to urbanconditions, prefers full sun

Red chokeberry

Inkberry

Blackhaw viburnumBayberry

16

Joe pye weed (Eupatorium fistulosum)5’-7’ tall with huge rounded purple flowers in August-September; prefers fullsun to partial shade, moist, wet soil;attracts butterflies (N)

Blazing star, spike gayfeather (Liatrisspicata) 3’ tall, upright, linear form; tallmauve-purple flower spikes summer-earlyautumn; requires sun; similar flower colorand habit to purple loosestrife but won’ttake wet soils; important nectar source formany insects and butterflies; cultivarsavailable with white-lavender flowers (N)

Beebalm (Monarda didyma) 2’-4’ tallwith red, pink, or white flowers in Julythrough August; requires full sun andmoist soils with no drought tolerance;attracts butterflies and hummingbirds

Garden Phlox (Phlox paniculata‘Robert Poore’ or ‘David’) - 2-3’ tallperennial, lavender or white flowersblooming throughout the summer; thrivesin full sun with good ventilation; resistantto powdery mildew that affects other cul-tivars (N)

Obedient plant (Physostegiavirginiana) 1 1/2 – 2’ tall with white orpink snapdragon-like flowers from June toSeptember over glossy foliage; prefers fullsun and acid soil, but not fussy, in fact, arampant grower in rich soil.

Blue vervain (Verbena hastata) 4-6’tall spikes of violet blue flowers in Julyand August; requires full sun and moistsoils (N)

New York ironweed (Vernonia novebo-racensis) 4 -7’ tall perennial whose flowersform a purple haze; grows well in full sun,moist locations, cut back after one monthif shorter plants are desired (N)

Solution

ProblemPurple loosestrifeLythrum salicaria

Purple loosestrife (Lythrum sali-caria) was introduced in the 1800’s forornamental and medicinal uses and isnow widely distributed in marshes andwet ditches in every state in the continen-tal U.S. except Florida. Purple loosestrife,a 3’-8’ tall herbaceous perennial, adaptswell to most sunny garden conditions butwill invade and displace native plants innearly any wet habitat. Wetland ecosys-tems are already significantly diminishedand threatened by other land use pres-sures. The magenta-colored flower spikesoccur throughout much of the summer,provide nectar for insects, and can pro-duce an incredible two to three millionseeds per plant per year that are readilydispersed by wind and water.

Alternatives to purple loosestrifeinclude:

Swamp milkweed (Asclepiasincarnata) 2-4’ tall with pink flowers inJuly through August; prefers full sun topartial shade, tolerates wet soils; attractsbutterflies (N)

17

Joe pye weedGarden phlox

Blazing star

Blue vervain New York ironweed

18

Korean feather reed grass(Calamagrostis brachytricha) - 3-4’ tall;clump-forming, upright-arching form;wide range of soils, part shade or full sun

Pink muhly grass (Muhlenbergia capil-laris) – 3’ tall with masses of delicate pinkflowers in late fall; marginally hardy inNorthern DE

Lindheimer’s muhly (Muhlenbergialindheimeri) - 3-4’ tall with 5’ flowerstalks; drought and heat tolerant;September blooms last through the win-ter; prefers full sun

Switchgrass (Panicum virgatum‘Dallas Blues’, P. virgatum ‘Cloud Nine’,P. virgatum ‘Northwind’) – 5 to 7’ tall;Dallas Blues has large purple panicles infall and wide blue foliage; Cloud Nine hasairy panicles that catch dew and frost; andNorthwind has a very sturdy verticalhabit; other cultivars available. (N)

Indiangrass (Sorghastrum nutans‘Sioux Blue’) – 5-6’ tall with arching habitand blue leaves; tan flowers with yellowpollen sacs are quite showy (N)

Frost grass (Spodiopogon sibiricus) – 4’ tall with a neatly rounded form, pani-cles produced in midsummer have smallhairs that catch the light; will grow inshade or full sun with adequate moisture

Solution

ProblemJapanese silver grassMiscanthus sinensis

Japanese silver grass (Miscanthussinensis) is a graceful ornamental grass,introduced from China, with many cultivars ranging in heights from 3’ to 9’.Flower heads are white to purple andflowering can occur from late summer to late fall. Cultivars that flower earlyhave time to set seed and can self-sowinto disturbed areas with open soil.Miscanthus ‘Purpurascens’ and Miscanthussinensis var. condensatus ‘Cabaret’ are twocultivars that are not known to set seed.

Alternative ornamental grassesinclude:

Silver bluestem (Andropogon ternarius)– 2’ tall with silvery inflorescences onslender stalks; purple bronze to copperred fall color; tolerates dry conditions (N)

Feather reed grass (Calamagrostis xacutiflora ‘Karl Foerster’ – 6’ tall with ver-tical inforescences that are loosely feath-ered in early summer and constrict to nar-row plumes by midsummer

19

Cloud nine switchgrass

Silver bluestem flowerFeather reed grass

Dallas blues switchgrass

Silver bluestem

20

Virginia creeper (Parthenocissusquinquefolia) – deciduous vine that willalso crawl across the ground; brilliantred fall color; tolerates just about anykind of soil and tough conditions, fullsun to full shade; fast growing (N)

Christmas fern (Polystichum acrosti-choides) – 1’ tall evergreen fern, toughand undemanding, grows in partial tofull shade (N)

Sweetbox (Sarcococca hookerianavar. humilis) – 1-2’ tall dense evergreenshrub that spreads by stolons and devel-ops into a colony; black berries and lus-trous green foliage; grows in partial tofull shade

Lowbush blueberry (Vacciniumangustifolium) – 6" to 2’ tall spreadingdeciduous shrub; white flowers, bluefruit and crimson fall color; toleratessandy, rocky, poor soils (N)

Barren-strawberry (Waldsteinia fra-garioides) – 6" with trifoliate, glossy,evergeen leaves; yellow flowers inspring; tolerates partial shade but fullsun is preferred (N)

Yellowroot (Xanthorhiza simplicissi-ma) – 2’ tall spreading (stolons)groundcover grows vigorously in wetsoils and slower in dry soils; toleratesfull sun to shade, somewhat inconspic-uous clusters of purple spring flowers(N)

Solution

ProblemPeriwinkleVinca minor

Periwinkle (Vinca minor) – is a vineor groundcover. A native of Europe, itgrows vigorously and forms a dense coverthat excludes most other plants, includingwoodland wildflowers. It only spreadsvegetatively so it poses the greatest threatwhen planted adjacent to a natural area.Its evergreen nature and vigorous growthare hard to replace in the garden.

Alternative groundcoversinclude:

Bearberry (Arctostaphylos uva-ursi) 6-12" tall glossy, evergeen groundcoverforming broad, thick mats; dainty flowersin May; does best in poor, sandy, infertile,acid soils; tolerates salt, prefers full sun,grows slowly (N)

White heath aster (Aster ericoides) – 1’ tall small-leaved aster with small whiteflowers in late summer to fall; prefers fullsun and average to dry soil (N)

Allegheny pachysandra (Pachysandraprocumbens) – 6-12" semi-evergreengroundcover with green to blue-greenmottled foliage; white-pink flower spikesin spring; tolerates partial to full shadebut grows slowly (N)

21

Sweet box

Christmas fern Allegheny pachysandra

Blueberry

22

grass-like leaves; tolerates shade or sunand wide range of soils

Plumbago, leadwort (Ceratostigmaplumbaginoides) 12" tall spreading groundcover; intense, dark-blue flowers in summer to late autumn; fall color is wonderful bronze-red; prefers sun to partial shade; works well with springbulbs as late developing foliage coversleaves of fading bulbs

Goldenstar (Chrysogonumvirginianum) dense ground cover to 10";deciduous dark green foliage; long lastinggolden yellow flowers in mid to latespring; grows in partial shade to full sun

Lily-of-the-valley (Convallariamajalis) vigorous, dense deciduousground cover to 8" tall, spreads by under-ground stems or rhizomes, arching stemsproduce scented, waxy, bell-shaped whiteflowers in spring; prefers partial shade orfull sun

Hay-scented fern (Dennstaedtia punctilobula) 2-3’ tall clump-formingdeciduous fern, dense, vigorous colonizer,tolerates poor soil and both shade andsun (N)

Geranium (Geranium x cantabrigiense'Biokovo' ) 8" tall, semi-evergreengroundcover, gently running and self-repairing, forming a neat green carpetovertopped by pink-tinged white flowersin May and June; thrives in full sun tolight shade and average to moist soils, butalso quite drought tolerant

Lilyturf, liriope (Liriope spicata, L. muscari) 18" tall, rhizomatous (L. spi-cata) or clump-forming (L. muscari)spreading, dark-green grass-like plant;spikes of lavender to white flowers in late

Solution

ProblemEnglish IvyHedera helix

English Ivy (Hedera helix), intro-duced by early European immigrants, isextremely popular and widely planted as adurable and dense, weed-excludinggroundcover with evergreen foliage. It ischallenging to match its dependability as a year-round ground cover. But, it is a serious threat to all vegetation levels offorested and open areas. It grows alongthe ground as well as into the tree canopy.Ivy spreads to neighboring properties byvegetative means and further a-field byspring-maturing seed dispersed by birdswhen other food sources are scarce.

Alternatives for English ivyinclude those suggested for periwinkle (Vinca minor) plus:

Wood aster (Aster divaricatus) 3’ tallby 2’ wide spreading, flowering perennial;white daisy-like flowers; prefers shade topartial shade and dry soil; good naturaliz-er under trees or as a filler with otherperennials (N)

Variegated sedge (Carex morrowii ‘SilkTassel’, or ‘Ice Dance’) - mounding to 1’in height, green and cream variegated

23

summer; full sun to shade; tolerant ofextreme heat and urban conditions

Variegated Solomon’s seal(Polygonatum odoratum ‘Variegatum’) 2’tall upright spreading deciduous plantwith arching stems and green and creamvariegated leaves; bell shaped flowershanging from leaf axils in spring; prefersshade to partial shade, tolerates wet to dry soils

(N) = native to Delaware Hay scented fern

Wood asterPlumbago

Wood aster Geranium

Authors:Susan Barton, University of DelawareGary Schwetz, Delaware Center forHorticulture

Project participants:Valann Budischak, University of DelawareJen Gochenaur, Delaware Nature SocietyFaith Kuehn, Delaware Department ofAgriculture

Photographs provided by:Susan BartonRick DarkeGary Schwetz

Graphic design by:Carrie Finnie

Funding provided by:National Fish and Wildlife Foundationthrough the Delaware Estuary GrantsProgram

Supported by:Delaware Center for Horticulture,Delaware Department of Agriculture,Delaware Invasive Species Council,Delaware Nursery and Landscape Assoc., University of Delaware

Acknowledgements