~ ~ ALABAMA A&M AND AUBURN UNIVERSITIES

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Weed Control in Residential Landscape Plantings

D esidentiallandscape plantings soften the archi­~ectural design of buildings, provide color and texture to the landscape, and increase the mone­tary and aesthetic value of property. Such plantings may be only several square feet in size or may occupy several thousand square feet. A single planting may consist of an individual plant, shrub, or tree or it may contain a complex layout of differ­ent ornamental shrubs, bulbs, ground covers, and flowers. It is the mixture of plant species in an ornamental planting that makes weed control diffi­cult, if not impossible. This publication will review the possible weed control alternatives available to homeowners and landscape managers.

Weeds are survivors or invaders of open habi­tats. The planting area is an ideal environment for the growth of weeds. The environment usually includes exposed or loosened soil, good availabili­ty of nutrient elements, and generally favorable moisture. While these factors favor good, healthy ornamental plant growth, they also aid in the growth of weeds.

Control Practices Four general practices can provide control of

most weed problems in residential landscape plantings. Control practices are measures that limit weed growth in desirable areas. Control practices usually result in a reduction in the sever­ity of weed problems rather than complete elimi­nation. The use of a single method of weed con­trol usually results in only partial success. Usually the most successful effort involves the use of two or more practices in a weed control effort. The four practices are sanitation practices; mechanical practices; cultural practices; and herbicide usage.

Sanitation Practices

seed, or plant material. Contaminated mulching materials are other possible sources of weed introduction. Examine all seed, plant material, mulches, and new soil before introducing them to a new planting area. If weeds, weed seed, or vegetative weed propagules (bulbs, tubers, or rhizomes, for example) are present, strongly consider using another material. Weeds are a lot easier to control before they are introduced than after they are established in a landscape planting.

Mechanical Practices Hand and mechanical removal of weeds are

the oldest methods of weed control. Hand pulling and hand hoeing are the safest and most effective and practical methods of control. These methods are most useful in small areas or in areas of mixed plantings of desirable ornamental plants where herbicide use would be impractical.

Mechanical control may also involve the use of tillers, edgers, or other equipment to remove existing weed problems. Tillers are useful in preparing a weed-free seedbed prior to planting as well as to remove small weeds emerging after planting. Shallow cultivation is useful in removing small weeds. Edgers remove marginal weeds that encroach on ornamental plantings.

Cultural Practices (Mulching) Mulching provides many benefits in orna­

mental plantings in addition to weed control. Mulching retains soil moisture, reduces erosion, reduces soil temperature, improves soil tilth, and suppresses weed seed germination and weed establishment. Mulching materials avail­able include straw, leaves, pine bark, old news­papers, and landscape fabric. These materials when used properly alone or in combination will shade the soil, preventing many weed seeds from germinating.

Sanitation practices involve the continuous use of weed-free seed, mulch materials, soil, and plant material in landscape plantings. No soil area in the landscape is completely devoid of Herbicide Usage weeds. And, new weed problems are frequently Chemicals used to control weeds are called introduced by using weed-contaminated soil, herbicides. The use of herbicides for weed

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control is only a short-term solution to a weed problem. Other control options such as mulching or mechanical removal offer safer and more long-term results. It is very important to select and use herbicides properly. Misapplica­tion of herbicides can cause them to fail to con­trol weeds, cause injury to ornamental plants, and even be dangerous in some situations. All herbicides labeled for use in landscape plant­ings have been tested by chemical companies and are approved for use by the Environmental Protection Agency (EPA). The herbicide label provides specific instructions for use and safety precautions and is the best source of informa­tion concerning the use of any product.

Generally, there are two opportunities to con­trol weeds in a landscape planting. Weeds can be controlled in some established plantings by apply­ing an herbicide to weed-free soil prior to the ger­mination of weed seeds and emergence of weed seedlings. This type of herbicide application is termed a preemergence application using a preemergence herbicide. The herbicides are effective only on soils that have no weed growth present, and they prevent the germination or emergence of some weeds. Preemergence herbi­cides do not control all weeds. The herbicide label identifies the spectrum of weeds controlled. These herbicides cannot be used around all orna­mental plants. It is important that you read the herbicide label and see that all ornamental plants in the planting are included on the label before purchasing and using the herbicide.

The other opportunity to control weeds is to apply a herbicide to emerged weeds present in the planting. This type of herbicide application is termed a postemergence application using a postemergence herbicide. Postemergence herbi­cides are effective in controlling small weeds that are actively growing at the time of treatment. Herbicides that can be applied safely over the top of some desirable plants (but kill target weeds) are termed selective herbicides. Selective paste­mergence herbicides for use around ornamental plants are few in number. Selective postemer­gence herbicides do not control all emerged weeds, so effective herbicides have to be matched with desirable ornamentals present. Herbicides that kill most or all plants treated are called non­selective herbicides. These products will severe­ly injure or kill desirable landscape plants.

Calibration To achieve maximum effectiveness from any

herbicide, it is critical that application equip-

2

ment be properly calibrated before using it to apply the recommended herbicide rate over the treatment area. Applying too little herbicide will give poor results, while applying too much herbicide will cause plant injury and excessive chemical cost. To apply a liquid herbicide spray uniformly, it is generally recommended that 20 to 40 gallons of spray solution be applied per acre of land (0.5 to 1 gallon of herbicide spray solution per 1,000 square feet of soil).

Herbicide Safety Before being sold to the public, all herbicides

are thoroughly tested to assure they are effective and safe when used properly according to label directions. By their nature, herbicides are toxic. Pesticides are placed in three categories based on toxicity: DANGER (highly toxic), WARNING (moderately toxic), and CAUTION (low toxicity). Most preemergence and postemergence herbi­cides are in the WARNING and CAUTION cate­gory. The herbicide label contains the toxicity category along with instructions to the user describing risk and benefits. The time taken to read the label is probably the most valuable time spent in weed control.

Herbicide Selection The selection of the correct herbicide is one

of the most critical decisions in developing an effective weed control program. It should include not only the weeds to be controlled and the plants that are to be treated, but also the environmental conditions and nontarget plants. Herbicide labels give valuable information as to the growth stage, time, and method of applica­tion for the target weed species. Many orna­mental species are listed on some labels, but because there are so many species and culti­vars, no herbicide has been tested on all possi­ble plants used in ornamental plantings. Use on species not listed on the label may result in damage to desirable plants. Trial usage should be limited to a small area.

The following are general characteristics of her­bicides labeled for use in ornamental plantings. This information is not meant to take the place of the specific herbicide label but is intended to offer use­ful information to aid in the selection process. Note: not all of the herbicides discussed are labeled for use by homeowners. Homeowners may use herbicides with the following common names: oryzalin oryzalin + benefin dichlobenil sethoxydim fluazifop-ethyl trifluralin glyphosate

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Common Name: bensulide

Trade Names: Formulation: Bensumec 4LF 4 lb./gal. liquid

Use: Preemergence-Landscape managers only Mode of Action: Inhibits the growth of weed roots. Manufacturers:

Bensumec-PBI Gordon Corp., Kansas City, Missouri

Common Name: clethodim Trade Name: Formulation:

Envoy 0.94lb./gal. emulsifiable concentrate

Use: Postemergence-Landscape managers only Mode of Action: Inhibits fatty acid synthesis and energy conversion. Manufacturer:

Valent USA Corp., Walnut Creek, California

Common Name: dichlobenil

Trade Names: Formulation: Casoron 4G 4% granule Barrier 4G 4% granule

Use: Preemergence-Homeowners and landscape managers Mode of Action: Inhibits growth of shoot and root tips. Manufacturers:

Casoron -Crompton-Uniroyal Chemical, Middlebury, Connecticut

Barrier-FBI Gordon Corp., Kansas City, Missouri

Common Name: fenoxapxop-ethyl

Trade Names: Formulation: Acclaim Extra 0.57 lb./gal. emulsifiable

concentrate Use: Postemergence grass control-Landscape man­agers only Mode of Action: Inhibits plant lipid synthesis. Manufacturer:

Bayer, Environmental Science, Montvale, New Jersey

Common Name: fluazifop-ethyl

Trade Name: Formulation: Ornamec 0.5 lb./gal. liquid Ornamec 170 0.125 lb./gal. liquid

Use: Postemergence grass control Grass-B-Gon-Homeowners Ornamec-Landscape managers only

Mode of Action: Kills shoot tips and rhizome buds in susceptible grasses. Manufacturer:

Ornamec-PBI Gordon, Kansas City, Missouri

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Common Name: glyphosate

Trade Name: Roundup Pro Roundup Weed and

Formulation: 4lb./gal. liquid (41 %)

Grass Killer Concentrate 18% liquid Eraser 18% liquid Hi-Yield Killzall 10% liquid

Use: Non-selective postemergence herbicide­Homeowners and landscape managers Mode of Action: Inhibits amino acid synthesis. Manufacturers:

Roundup-Monsanto Chemical Co., St. Louis, Missouri

Hi-Yield Killzall-Hi-Yield Chemical Co., Bon­ham, Texas

Surrender Brand Eraser Control Solutions, Inc., Pasadena, Texas

Common Name: isoxaben

Trade Name: Formulation: Gallery 75DF 75% dry flowable

Use: Preemergence herbicide-Landscape man­agers only Mode of Action: Disrupts shoot and root develop­ment. Manufacturer:

Dow AgroSciences, Indianapolis, Indiana

Common Name: isoxaben + trifluralin

Trade Name: Formulation: Snapshot 2.5 TG 2.5% granule

Use: Preemergence herbicide-Landscape man­agers only Mode of Action: Disrupts processes associated with seed germination and shoot and root development. Manufacturer:

Dow AgroSciences, Indianapolis, Indiana

Common Name: metolachlor

Trade Name: Formulation: Pennant Magnum 7.62 lb./gal. liquid Pennant Liquid 8 lb./gal. liquid

Use: Preemergence herbicide-Landscape man­agers only Mode of Action: Inhibits general weed seedling growth, especially root elongation, and may disrupt membrane integrity. Manufacturer:

Syngenta Crop Protection, Greensboro, North Carolina

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Common Name: oryzalin

Trade Names: Formulation: Surflan A.S. 4 lb./gal. flowable Use: Preemergence herbicide-Homeowners and

landscape managers Mode of Action: Disrupts processes associated with seed germination. Manufacturer:

Dow AgroSciences, Indianapolis, Indiana

Common Name: oryzalin + benefin

Trade Name: Formulation: XL 2G 2% granule

Use: Preemergence herbicide-Homeowners and landscape managers Mode of Action: Disrupts growth processes associ­ated with seed germination. Manufacturer:

Dow AgroSciences, Indianapolis, Indiana

Common Name: oryzalin + oxyfluorfen

Trade Name: Formulation: Rout 3G 3% granule (2% oxyfluor-

fen + 1 o/o oryzalin) Use: Preemergence-Landscape managers only Mode of Action: Disrupts processes associated with seed germination. Manufacturer:

Scotts-Sierra Crop Protection Co., Maryville, Ohio

Common Name: oxadiazon

Trade Name: Formulation: Ronstar G 2% granule

Use: Preemergence-Landscape managers only Mode of Action: Inhibits the growth of young shoots by contact action. Manufacturer:

Bayer Environmental Science, Montvale, New Jersey

Common Name: pendimethalin

Trade Names: Pendulum WDG

Formulation: 60% water dispersal granule

Pendulum 2G 2% granule Pendulum 3.3EC 3.3 lb./gal. liquid Lesco Pre-M 3.3EC 3.3 lb./gal. liquid Lesco Pre-M 60WP 60% wettable powder

Use: Preemergence herbicide-Landscape managers only Mode of Action: Inhibits cell division and elonga­tion, especially in weed seedling roots. Manufacturers:

Pendulum-BASF Corporation, Parsippany, New Jersey

Lesco Pre-M-LESCO, Inc., Rocky River, Ohio

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Common Name: prodiamine

Trade Name: Formulation: Barricade 65WG 65% water dispersible

granule Barricade 4FL 4 lb./gal. liquid

Use: Preemergence-Landscape managers only Mode of Action: Prevents seed germination and inhibits root growth in sensitive weeds. Manufacturer:

Syngenta Crop Protection, Greensboro, North Carolina

Common Name: sethoxydim

Trade Names: Formulation: Vantage 1 lb./gal. liquid

Use: Postemergence herbicide-Homeowners and landscape managers Mode of Action: Interferes with lipid metabolism. Manufacturer:

Top Pro Specialties, Memphis, Tennessee

Common Name: trifluralin

Trade Name: Formulation: Treflan 56 5% granules Preen 1.4 7% granule

Use: Preemergence herbicide. Preen-Homeowners Treflan-Landscape managers only Mode of Action: Adversely affects growth process­es associated with seed germination. Manufacturers:

Preen-Lebanon Chemical Corp., Lebanon, Pa. Treflan-Dow AgroSciences, Indianapolis,

Indiana

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Table 1. Weeds Controlled by Herbicides Labeled for Use in Residential Landscape Plantings Herbicides To Use (See Legend)

Weeds

barnyardgrass bermudag1·ass

betony, Florida bittercress bluegrass, annual ca.rpetweed chamber bitter

chickweed

crabgrass dodder geranjum, Carolina goosegrass henbit Jambsquarter nutsedge, yellow pig\'lleed pul"slane

pusley, Florida ragweed, common

ryegTass, annual sand bur sheperdspurse spurge

torpedograss woodsorrel

LEGEND A = bensulide * B = clethodim * C = dichlobenil D = fenoxaprop * E = fluazifop * F = glyphosphate G = isoxaben * H = isoxaben + tirfluralin * I = metolachlor *

A

X

X

X

X

X

X

X

B c D E

X X X

X X X

X

X X

X

X

X X X X

X X X

X

X

X

X

X

X

X X X

X

X

X

X

F G H I J K L

X X X X X X

X

X

X X X X

X X X X X X

X X X X X

X X X

X X X X X X

X X X X X X

X X X

X X X X X

X X X X X

X X X X X

X X

X X X X X X

X X X X X X

X X X

X X X

X X X X X

X X X

X X X X X

X X X X X

X

X X X X X

J = oryzalin K = oryzalin + benefm L = oryzalin + oxyfluorfen * M = oxadiazon * N = pendimethalin * 0 = prodiamine * P = ethoxydim Q = trifluralin

* Product labeled for use only by residential landscape managers

5

M N 0 p Q X X X X X

X

X

X X X X

X X X X

X

X X X

X X X X X

X X X X X

X X

X X X X

X X X X

X X X X

X X

X

X X X

X X X

X X X

X X X

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Table 2. Herbicides Labeled for Ornamental Bulbs, Annuals, Herbaceous Perennials, and Ground Covers Growing in Residential Landscape Plantings

A B c Bulbs daffodils (na1·cissus) X

gladiolus X

hyacinth iris, bulbous X

tulip X

Annuals and Herbaceous Perennials babysbreath blackeyed Susan daisy, Shasta day lily marigold pansy peony petunia snapdragon sweet William zinnia, common

Ground Covers buglew eed ivy, English jasmine, Asiatic liriope mondo grass periwinkle , bigleaf pe1iwinkle, common

LEGEND A = bensulide * B = clethodim * C = dichlobenil D = fenoxaprop • E = fluazifop * F = glyphosphate G ~ isoxaben • H = isoxaben + tirfluralin * I = metolachlor *

X

X

X

X X

X

X

X

X

X

X X

X X X

X

X

X

X

X X

D

X

X

X

X

X

X

X

X

X

X

X

E

X

X

X

X

X

X

X

X

X

X

X

Herbicide To Use (See Legend) F G H I J K L

X X X X

X

X X X X

X X X X

X X X X

X

X X X X

X X

X X

X

X X

X

X X X X X

X X

X X X X X

X X X X

X X

X X X X X

J = oryzalin K ~ oryzalin + benefm L = oryzalin + oxyfluorfen * M ~ oxadiazon * N = pendimethalin * 0 = prodiamine * P = ethoxydim Q = trifluralin

M N

X

X

X

X X

X

X

X

X X

• Product labeled for use only by residential landscape managers

6

0 p Q

X

X

X X

X

X X

X X

X X

X X

X X

X

X X

X

X X

X X

X

X X

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Table 3. Herbicides Labeled for Ornamental Shrubs and Trees Growing in Residential Landscape Plantings

Shrubs arborvitae azalea barbeny boxwood camellia cleyera, Japanese crapemyrtle euonym.us fire thorn forsythia gardenia holly hydrangea jessamine, Carolina

juniper lantana lilac oleander podocarpus privet red tip rhododendron rose viburnum waxmyrtle weigela yew

Trees dogwood, flowering magnolia, southern maple, red oak olive, Russian redbud red cedar, Eastern

LEGEND A = bensulide * B = clethodim • C = dichlobenil D = fenoxaprop * E = fluazifop * F - glyphosphate G = isoxaben * H = isoxaben + tirfluralin • I = metolachlor *

A

X

X

X

X

X

X

X

B c D E

X

X X X

X X

X X X X

X X X

X X

X

X X X X

X X X X

X X X

X X X

X X X X

X X

X

X X X X

X X

X

X X

X

X X X X

X X X X

X X X X

X X X X

X X

X

X X

X X X

X X X X

X X

X X X

X X

X X X

X

X

Herbicide To Use (See Legend) F G H I J K L

X X X X

X X X X X

X X X X

X X X X X X

X X X X

X X X X

X X X X X

X X X X X X

X X X X X

X

X X X X X

X X X X X X

X

X X X

X X X X X X

X X X

X X X X

X X X X X

X X X X X X

X X X X X X

X X X X X X

X X X X X X

X X

X X X X

X X X

X X X X X

X X X X

X X X X X

X X X X X

X X X X

X X X X X

X X X X

X X X X

X X X X X

J oryzalin K oryzalin + benefm L = oryzalin + oxyfluorfen • M = oxadiazon • N = pendimethalin * 0 = prodiamine • P ethoxydim Q = trifluralin

M N

X

X X

X X

X X

X X

X X

X X

X

X

X X

X X

X X

X X

X X

X

X X

X X

X

X

X

X

X X

X X

X X

X X

X

X

X X

• Product labeled for use only by residential landscape managers

7

0 p Q

X

X

X X X

X X X

X X

X

X X

X

X X X

X

X X

X X X

X

X

X X X

X

X

X

X

X X X

X X

X X

X

X X X

X

X X

X X X

X

X

X X

X

X

X ARCHIVE

ORNAMENTAL PLANTS Bulbs daffodils gladiolus hyacinth iris, bulbous tulip

Narcissus spp. Gladiolus x hortulanus Hyacinthus orientalis Iris spp. Tulipa spp.

Annuals and Herbaceous Perennials babysbreath Gypsophilia elegans blackeyed Susan Rudbeckia hirta

daisy, Shasta day lily marigold pansy peony petunia snapdragon sweet William zinnia, common

Ground Covers

var. pulcherrima Chrysanthemum x superbum Hemerocallis spp. Tagetes spp. Viola x wittrockiana Paeonia spp. Petunia x hybrida Antirrhinum majus Dianthus barbatus Zinnia elegans

bugleweed Ajuga spp. ivy, English Hedera helix jasmine, Asiatic Trachelospermum asiaticum liriope Liriope spp. mondo grass Ophiopogon japonicus periwinkle, bigleaf Vinca major periwinkle, common Vinca minor

Shrubs arborvitae Arborvitae spp. azalea Rhododendron spp. barberry Berberis spp. boxwood Buxus spp. camellia Camellia spp. cleyera, Japanese Ternstroemia gymnanthera crapemyrtle Lagerstroemia indica euonymus Euonymus spp. flrethorn Pyracantha spp. forsythia Forsythia spp. gardenia Gardenia spp. holly !lex spp. hydrangea Hydrangea spp. jessamine, Carolina Gelsemium sempervirens juniper juniperus spp. lantana Lantana spp. lilac Syringa spp.

oleander red tip podocarpus privet rhododendron rose viburnum waxmyrtle weigela yew

Trees dogwood, flowering magnolia, southern maple, red oak olive, Russian redbud red cedar, eastern

WEEDS barnyardgrass bermudagrass betony, Florida bittercress bluegrass, annual carpetweed chamber bitter chickweed crabgrass dodder geranium, Carolina goose grass hen bit lambsquarter nutsedge, yellow pigweed purslane, common pusley, Florida ragweed, common ryegrass, annual sand bur sheperdspurse spurge torpedograss woodsorrel, yellow

Nerium oleander Photinia spp. Podocarpus spp. Ligustrum spp. Rhododendron spp. Rosa spp. Viburnum spp. Myrica cerifera Weigela spp. Taxus spp.

Comus florida Magnolia grandif[ora Acer rubrum Quercus spp. Elaeagnus angustifolia Cercis canadensis Juniperus virginiana

Echinochloa crus-galli Cynodon dactylon Stachys floridana Cardamine hirsuta Poa annua Mollugo verticillata Phyllanthus urinaria Stellaria media Digitaria spp. Cuscuta spp. Geranium carolinianum Eleusine indica Lamium amplexicaule Chenopodium album Cyperus esculentus Amaranthus spp. Portulaca oleracea Richardia scabra Ambrosia artemisiifolia Lolium multif[orum Cenchrus spp. Capsella bursa-pastoris Chamaesyce spp. Panicum repens Oxalis stricta

> ~ Jbohnh WA. Ebverest,. Ext~nsion Weed Scientist, Professor, Agronomy and Soils, and]. David Williams, Extension Horticulturist Professor Horticulture

ot at u unz Umversl ' ' .

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ANR-854

~se pesticides only accordi~g to the directions on the labeL Follow all directions, precautions, and restrictions that are listed. Do not use pesti· C1des on plants that are not hsted on the label.

The pesticides in t~is publication are :ecommended only if they are registered with the Environmental Protection Agency or the Alabama Department of Ag~1c_ulture and l~dustnes. If a registration is changed or cancelled, the product listed here is no longer recommended. Before you apply any peshcJde, check w1th your county Extension agent for the latest information

Trade names are used only to give specific information. The Alabama Cooperative Extension Service does not endorse or guarantee any product and does not recommend one product instead of another that might be similar

l'or m~rc in(or.mution. Ciill )'Our county Extension orru~e. Look In your telephone directory under your county's nnrnc IO find the number Issued tn furtherance of ~ooperativ~ Extension work, Acts of May 8 and June 30, 1914, in cooperation wHh the U .S. Department of Agricul~ture by the Alabama Cooperative ExtensiOn System (Alabama A&M University and Auburn University) . '

10M13, Revised July 2003, ANR-854

© 2003 by the Alabama Cooperative Extension Sysrem AJI rights reserved

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