Controlling Weeds in Nursery and Landscape Plantings

Stability on soil: High. Low leaching potential.

Mode of action: Absorbed mostly by roots, but may be absorbed by soft, new growth of both weeds and trees. It translocates to leaves and growing points, where it inhibits photosynthesis.

Crop uses: Newly planted and established field-grown Christmas trees.

Weed control strengths: Controls most broadleaved weeds and some annual grasses. Provides some control of established fine fescues, including hard fescue. Provides some postemergence control of annual weed seedlings.

Weed control weaknesses: Does not provide control of annual grasses for long periods.

Notes: May be applied over the top of trees before budbreak. After budbreak, apply as a directed spray. Aatrex is a restricted use product.

Stability on soil: High, but inactivated by soils containing high amounts of organic matter; temperature stable; slight photodecomposition.

Mode of action: Inhibits root growth.

Crop uses: Established turfgrass, ornamentals, bulbs, other flowers, and ground covers.

Weed control strengths: Controls annual grasses and some broadleaved weeds.

Weed control weaknesses: Does not control many annual broadleaved weeds.

Notes: Apply under mulch and activate with one-half inch of irrigation immediately after application. Use on mineral soils only.

Stability on soil: Low; evaporates rapidly from moist soils at high temperatures. To ensure herbicide activity, apply in cool weather (below 45 degrees F) just before a rainfall, or follow application with irrigation, cultivation, or mulching. Leaching potential is low on fine-textured soils (clay) and moderate on coarse-textured soils (sandy).

Mode of action: Acts primarily on growing points and root tips, inhibiting growth of meristems. Upward translocation of root-absorbed dichlobenil is rapid. Leaves can easily absorb its vapors.

Crop uses: Established landscape and field-grown woody ornamentals, nut and fruit trees, and noncropland.

Weed control strengths: Preemergence control of annual and perennial broadleaved and grassy weeds. One of the few preemergence herbicides that will control established winter annual and perennial weeds. The best material for controlling mugwort (chrysanthemum weed). Other established perennial weeds controlled or suppressed include field horsetail (Equisetum), tall fescue, orchardgrass, wild carrot, yellow nutsedge, quackgrass, and bindweed.

Weed control weaknesses: Does not provide good preemergence weed control far into the growing season.

Notes: Apply under mulch. Do not make surface application to areas cultivated during the fall or summer before application; do not use for 4 weeks after transplanting, 6 months after cuttings root or after planting rooted cuttings. Do not use on light, sandy soils. Do not allow granules to accumulate and contact trunk at or below the soil line. Do not use on hollies, firs, hemlocks, and spruce or on pines that have been established for less than 2 years. Dichlobenil can move downhill - use with caution on slopes.

Stability on soil: Medium to low. Little is lost to volatilization, but photodecomposition can occur from high-intensity sunlight. Low leaching potential.

Mode of action: Unknown. Inhibits development and growth of germinating weeds.

Crop uses: Landscape, field, liner, and container-grown ornamentals, including ground covers, flowers, and warm-season turf.

Weed control strengths: Controls most annual grasses and some broadleaved weeds, including chickweed.

Weed control weaknesses: Does not control a broad spectrum of annual broadleaved weeds.

Notes: Apply under mulch. Apply to newly planted container stock after soil is settled from first watering. Best applied in fall or early spring. Summer applications should be covered with a mulch or incorporated with irrigation shortly after application. The sooner water is applied (rainfall or irrigation) after application, the better the control.

Stability on soil: Low; readily lost to volatilization if not incorporated. Medium to high leaching potential.

Mode of action: Readily absorbed by roots and translocated upward; inhibits growth in meristematic regions.

Crop uses: Landscapes, field-grown ornamentals, ground covers, and flowers.

Weed control strengths: Controls annual grasses, some annual broadleaved weeds, and a few perennial weeds (including quackgrass and yellow nutsedge).

Weed control weaknesses: Does not control some annual broadleaved weeds or most perennials. The length of preemergence control is relatively short. For best results it must be incorporated 2 to 6 inches into well-prepared soil.

Notes: Apply under mulch. Use only on mineral soils. Do not store near seeds or fertilizers. Do not use on flowering bulbs, salvia, phlox, snapdragon, and ornamental peppers as injury may occur.

Stability on soil: Medium (photodecomposition and volatilization). Strongly adsorbed by soil, not readily leached.

Mode of action: Prevents seed germination. Absorbed through roots and inhibits root and shoot growth.

Crop uses: Barricade - ornamental trees, shrubs, flowers, turf in landscapes. Endurance - ornamental trees, shrubs, and flowers in landscapes; seedling nurseries; noncrop areas. Factor - container and field-grown ornamental trees, shrubs, herbaceous perennials, and bulbs; seedling nurseries.

Weed control strengths: Controls most annual grasses and some broadleaved weeds.

Weed control weaknesses: Does not control many annual broadleaved weeds.

Notes: Apply under mulch. Should be incorporated with cultivation, rainfall, or irrigation within 14 days of application. May be applied over the top of many ornamentals. Do not apply more than 1.5 lb ai/A per year.

Stability on soil: High. Low leaching potential.

Mode of action: Appears to disrupt root and hypocotyl development, killing susceptible plants prior to emergence from the soil. Very little absorption through foliage.

Crop uses: Established landscape, field, and container-grown woody and herbaceous ornamentals; ground covers; some bulbs; ornamental grasses; and turf.

Weed control strengths: Preemergence control of most broadleaved weeds with some suppression of annual grasses.

Weed control weaknesses: Does not control velvetleaf, mallow, morningglory, cutleaf evening primrose, nutsedge, or annual grasses.

Notes: Apply under mulch. May be applied over the top of many ornamental plants. Do not use on bedding plants. Do not apply to ground covers until they are well rooted. Soil or growing medium must be irrigated and well settled before applying to recently transplanted stock. Do not use on Euonymus alatus, lilacs, hydrangea spp, ajuga, iberis, sedum, euphorbia, and mustards. Should be incorporated with cultivation, rainfall, or irrigation within 21 days of application. Snapshot TG is a premixed granular combination of Gallery + Treflan.

Stability on soil: Medium to high. Low leaching potential.

Mode of action: Forms a chemical barrier on the soil surface. As weeds grow through it, they are burned off through contact activity. Light is required for activity.

Crop uses: Conifer seedbeds, transplants, container stock, and selected field-grown deciduous trees.

Weed control strengths: Provides excellent control of most broadleaved weeds and many grasses from seed. One of the few preemergence herbicides that can provide very good postemergence control of weeds up to 4 inches tall. Controls mile-a-minute weed.

Weed control weaknesses: Does not provide complete control of emerged grasses or large broadleaved weeds. Does not control horseweed. Annual grasses are the first weeds to begin growing in areas treated with Goal.

Notes: Apply over the top of mulch. Goal needs light to be active. Covering with a mulch or incorporating it will inactivate it. Anything that breaks the chemical barrier (like cultivation) will reduce its effectiveness. Goal can be applied to conifer seedbeds prior to emergence of the conifers. After emergence, wait a minimum of 5 weeks before applying over the top of the conifers. For postemergence control, add 0.25% nonionic surfactant and apply to weed seedlings less than 4 inches tall. Goal can burn the soft growth of broadleaved ornamentals it directly contacts. Premixed combinations include OH2 (Goal + Pendulum), Rout (Goal + Surflan), and Regal O-O (Goal + Ronstar). All are produced as granular formulations. Combine Goal 2XL with Vantage to control broadleaved and grass weed seedlings.

Stability on soil: High. High leaching potential.

Mode of action: Inhibits the production of certain amino acids; kills growing points first.

Crop uses: Landscape ornamentals and warm-season turfgrass.

Weed control strengths: Preemergence and postemergence control of broadleaved weeds such as Carolina geranium, henbit, chickweed, and buttercup; wild garlic and onion; yellow and purple nutsedge; and some grasses.

Weed control weaknesses: Not labeled for many ornamental species. Does not control many annual or perennial grasses or some broadleaved weeds.

Notes: Do not apply to unlabeled ornamentals, cool-season turf, annual bedding plants, or container-grown ornamentals.

Stability on soil: Medium to high. Loss through photodecomposition and volatilization is highly dependent on temperature. Leaching potential medium to low.

Mode of action: Absorbed through the roots, translocated upward; inhibits growth. Not absorbed through foliage.

Crop uses: Field-grown woody ornamentals.

Weed control strengths: Preemergence and early postemergence control of winter annual and perennial grasses, such as quackgrass, and some winter annual broadleaved weeds. One of the few preemergence herbicides that provide control of established perennial weeds. Kerb is the best material for controlling fine fescues (red, hard, sheeps, and chewings).

Weed control weaknesses: Does not provide preemergence control far into the spring.

Notes: Apply under mulch. Apply in the fall after the temperature will stay below 55 degrees F but before the soil freezes. Do not apply to seedlings or transplants less than 1 year old. Kerb is a restricted use product.

Stability on soil: Medium to high. Low leaching potential.

Mode of action: Oxyfluorfen acts as a contact herbicide and requires light for activation; pendimethalin inhibits root development.

Crop uses: Field and container-grown woody ornamentals and ground covers.

Weed control strengths: Controls most annual weeds.

Weed control weaknesses: Few.

Notes: Apply over the top of mulch. Do not apply while plants are producing a new flush of spring growth. Do not apply in extreme cold temperatures. Irrigate after application to wash granules from the foliage and activate the herbicide. Soil particles splashed onto low foliage by coarse irrigation or heavy rainfall can carry enough herbicide to severely injure low-growing sensitive plants. Laying down a light mulch prior to the herbicide application will prevent this problem. Not recommended for field liner beds, but may be used on potted bareroot liners 3 to 4 weeks after potting.

Stability on soil: Medium to high. Slight losses from photodecomposition and volatilization. Low leaching potential.

Mode of action: Inhibits root growth through inhibition of cell division and cell elongation.

Crop uses: Field or container-grown woody ornamentals, landscapes, ground covers, herbaceous perennial and annual flowers, ornamental grasses, and turf.

Weed control strengths: Controls most annual grasses and some broadleaved weeds.

Weed control weaknesses: Does not control many annual broadleaved weeds.

Notes: Apply over or under mulch, preferably under. Stains equipment and anything else it contacts. Should be incorporated by cultivation, rainfall, or irrigation within 14 days of application. Delay application to potted bareroot liners 2 to 4 weeks after transplanting. Plants in field liner beds must be well rooted with the soil firmed prior to use. May be used over the top of many ornamental species. OH2 is a premixed granular formulation of Goal and Pendulum.

Stability on soil: Medium. Volatilization may occur under hot, moist conditions. Medium to high leaching potential.

Mode of action: General growth inhibitor, especially of root elongation. Germinating monocot seedlings absorb metolachlor through the shoots just above the seed, whereas dicots absorb it through both shoots and roots; may inhibit protein synthesis.

Crop uses: Landscape, field, and container-grown woody and herbaceous perennials; ground covers; bulbs; annual flowers; liner or transplant beds; and nonbearing fruit trees. Granular formulation can also be used on turf.

Weed control strengths: Best preemergence herbicide for control of yellow nutsedge. Also controls many annual grasses and some broadleaved weeds.

Weed control weaknesses: Does not control many annual broadleaved weeds.

Notes: Apply either over or under mulch. Do not apply to seedbeds or cutting beds before transplanting. Do not make more than two applications per year. Wash from foliage to reduce the chance of injury when applied over the top.

Stability on soil: Medium. Loss from photodecomposition and volatilization can occur when exposed on the soil surface. Medium to low leaching potential.

Mode of action: Inhibits photosynthesis by interfering with the development of carotenoids, a plant pigment that protects chlorophyll.

Crop uses: Field-grown nursery stock. Not recommended for any conifers except juniper.

Weed control strengths: Controls many annual grasses and broadleaved weeds and suppresses others including nutsedge.

Weed control weaknesses: Few.

Notes: Do not apply until the fall following the first full season of growth in the field after transplanting. Make only one application per year. Use only on medium- and fine-textured soils; do not apply to coarse-textured soil. Apply as a directed spray to avoid contact with foliage. Should be incorporated by cultivation, rainfall, or irrigation within 4 weeks.

Stability on soil: High. Low leaching potential.

Mode of action: Absorbed mostly through roots; translocated to leaves and growing points, where it inhibits photosynthesis.

Crop uses: Field or container-grown nursery stock and landscapes.

Weed control strengths: Controls most broadleaved weeds and some annual grasses. Can control annual broadleaved weeds in the dormant rosette stage.

Weed control weaknesses: Does not provide control of annual grasses for long periods. Does not control velvetleaf. After several years of use, resistant types of normally sensitive weeds may develop.

Notes: Apply under or over the top of mulch, preferably under. Use lower rates on coarser-textured soils and soil low in organic matter. Do not apply for 1 year after transplanting. Do not apply to Christmas trees less than 2 years old. Do not apply more than 4 pounds of active ingredient per acre in a year.

Stability on soil: High. Low leaching potential.

Mode of action: Oxadiazon forms a chemical barrier on the soil surface. As weeds grow through it, they are burned off through contact activity. Prodiamine is a root inhibitor.

Crop uses: Landscape, field, and container-grown woody ornamentals.

Weed control strengths: Preemergence control of annual grasses and broadleaved weeds.

Weed control weaknesses: Few.

Notes: Apply over the top of mulch. Needs light to be active. Covering with a mulch or incorporating it will inactivate it. Anything that breaks the chemical barrier will reduce its effectiveness. Soil particles splashed onto low foliage by coarse irrigation or heavy rainfall can carry enough herbicide to severely injure low-growing, sensitive plants. Laying down a light mulch prior to the herbicide application will prevent this problem. Do not apply to wet foliage or under conditions in which granules will collect on leaves.

Stability on soil: High. Low leaching potential.

Mode of action: Forms a chemical barrier on the soil surface. As weeds grow through it, they are burned off through contact activity.

Crop uses: Landscape, field, and container-grown woody ornamentals.

Weed control strengths: Preemergence control of annual grasses and broadleaved weeds.

Weed control weaknesses: Few.

Notes: Anything that breaks the chemical barrier will reduce its effectiveness. Soil particles splashed onto low foliage by coarse irrigation or heavy rainfall can carry enough herbicide to severely injure low-growing, sensitive plants. Laying down a light mulch prior to the herbicide application will prevent this problem.

Stability on soil: High. Low leaching potential.

Mode of action: Forms a chemical barrier on the soil surface. As weeds grow through it, they are burned off through contact activity. The sprayable formulation can kill existing weeds if they are thoroughly covered.

Crop uses: Landscape, field, and container-grown woody ornamentals; liners; conifer seedbeds; ground covers; some herbaceous ornamentals; and turf.

Weed control strengths: Preemergence control of annual grasses and broadleaved weeds. The 50WP formulation will control some emerged weeds.

Weed control weaknesses: Does not control spurge or chickweed from seed.

Notes: Apply over the top of mulch. Ronstar needs light to be active. Covering with a mulch or incorporating it will inactivate it. Anything that breaks the chemical barrier will reduce its effectiveness. The WP formulation can cause foliar damage; use as a directed spray only. Soil particles splashed onto low foliage by coarse irrigation or heavy rainfall can carry enough Ronstar to severely injure low-growing, sensitive plants. Laying down a light mulch prior to the herbicide application will prevent this problem. Regal O-O is a premixed granular combination of Goal and Ronstar.

Stability on soil: Medium to high. Low leaching potential.

Mode of action: Oxyfluorfen acts as a contact herbicide and requires light for activation; oryzalin inhibits root growth.

Crop uses: Field, landscape, and container-grown ornamentals; some ground covers and flowers.

Weed control strengths: Controls most annual weeds.

Weed control weaknesses: Few.

Notes: Apply over the top of mulch. Do not apply to plants with leaves that channel granules to the leaf base. Do not apply 2 weeks before or after leaf bud break; do not apply within 2 months of using other herbicides. Do not apply more than two applications per season. Soil particles splashed onto low foliage by coarse irrigation or heavy rainfall can carry enough herbicide to severely injure low-growing, sensitive plants. Laying down a light mulch prior to the herbicide application will prevent this problem. Cultivation or covering with a mulch will inactivate the Goal component of Rout.

Stability on soil: Low. No significant losses of isoxaben through photodecomposition or volatilization, but trifluralin can be lost through both. Low leaching potential.

Mode of action: Isoxaben appears to disrupt root and hypocotyl development but this has not been documented; trifluralin inhibits root growth.

Crop uses: Field, landscape, and container-grown ornamentals including ground covers, bulbs, herbaceous perennials, ornamental grasses, and nonbearing fruit trees.

Weed control strengths: Controls most annual broadleaved weeds and grasses.

Weed control weaknesses: Few.

Notes: Apply under mulch. See notes for isoxaben and trifluralin. Applications of 150 lb per acre should not be made less than 60 days apart. Do not apply more than 600 lb per acre in a 12-month period. Do not apply within 3 weeks of enclosing overwintering structures. Users who want to try this product on plants not on the label are permitted by the label to use Snapshot TG on small groups of plants prior to using it on a larger scale. Many growers have found this to be a suitable product for use on a wide variety of herbaceous perennial plants not on the label. However, the user assumes all risk associated with these applications.

Stability on soil: High. Minimal losses from photodecomposition and volatilization occur. Low leaching potential.

Mode of action: No significant absorption or translocation. Affects physiological growth processes associated with seed germination; inhibits root growth.

Crop uses: Established field, landscape, and container-grown ornamentals, including some ground covers, herbaceous perennials, bulbs, annual flowers, and warm season turf. It may be used to control weeds in the floors of open polyhouses, but not in enclosed structures. Do not apply within 3 weeks of covering polyhouses.

Weed control strengths: Controls annual grasses and some broadleaved weeds.

Weed control weaknesses: Does not control many annual broadleaved weeds.

Notes: Apply over or under mulch, preferably under. Do not use on soils containing more than 3% organic matter; do not use on conifer seed and transplant beds. Do not apply to pots less than 4 inches wide or to newly planted material until the soil or potting mix is settled by packing and irrigation. Do not use on slender deutzia, Douglas fir, Techny arborvitae, eastern hemlock, begonia, or coleus. Premixed combinations include Rout (oxyfluorfen + oryzalin) and XL (oryzalin + benefin). Rout controls both broadleaved weeds and grasses; XL controls most grasses but few broadleaved weeds.

Stability on soil: Low (photodecomposition and volatility). Low leaching potential.

Mode of action: No significant absorption or translocation. Affects seed germination by inhibiting root growth.

Crop uses: Landscape, field, and container-grown woody ornamentals; liners; herbaceous perennials; ground covers; bulbs; and annual flowers. More annual flowers are on this label than on any other preemergence herbicide label.

Weed control strengths: Controls most annual grasses and some broadleaved weeds.

Weed control weaknesses: Does not control many annual broadleaved weeds.

Notes: Apply under mulch. Not recommended for muck soils. For best results, cover with a mulch or irrigate within a few hours of application. Can be applied and mechanically incorporated prior to planting. Use lower rates (maximum 2 pints) if mechanically incorporated and higher rates if incorporated with irrigation. Typar Biobarrier is made with pellets that slowly release trifluralin into the soil to prevent root growth in certain areas for up to 20 years.

Stability on soil: oryzalin, high; benefin, medium (photodecomposition). Low leaching potential.

Mode of action: Inhibits root growth.

Crop uses: Established warm season turfgrass; landscape, field, and container-grown ornamentals, including some annual flowers and bulbs and ground covers.

Weed control strengths: Controls most annual grasses and some broadleaved weeds.

Weed control weaknesses: Does not control many annual broadleaved weeds.

Mulch: Apply over or under mulch, preferably under.

Notes: Do not use on the cool season turfgrasses common in the Northeast. Read the notes for Surflan.