Established Tree, Shrub, Rose, and Ground Cover Landscapes
Multiply rate by 0.023 for amount per 1,000 sq ft
geo-textiles
Available at agricultural and garden supply stores
Spun-bonded fabrics (non-woven) lightweight, extruded polypropylene fibers; requires mulch cover due to moderate UV light sensitivity; weed roots and rhizomes can penetrate fabric unless removed before establishment; cheapest option.
Woven fabrics moderate-weight polypropylene fibers woven into a mat; can be used without mulch cover due to UV light stability; weed roots and rhizomes can penetrate fabric although tightness of weave can prevent some weeds; moderate cost.
Laminates highly porous, dense poly film bonded to capillary fibers with a pressed, non-woven bottom layer. Surface is slick and causes rapid wetting and drying to prevent weed establishment except for perennial rhizomes that can penetrate the laminate; most expensive geo-fabric.
ESTABLISHED LANDSCAPES—Soil-applied
DCPA (Dacthal)
Rate 4.5 to 10.5 lb ai/A (6 to 14 lb/A) depending on soil type and target weeds
Time Apply to weed-free soil in early spring or late summer for control of susceptible winter weeds for annual weed control.
Remarks Performs erratically west of the Cascades. Sprinkler-irrigate after application to activate herbicide. Inhibits mitosis in roots and shoots.
Site of action Group 3: microtubule assembly inhibitor
Chemical family Phthalic acid
dichlobenil (Casoron 4G)
No ground covers
Rate 4 to 6 lb ai/A (100 to 150 lb/A granular product)
Time Apply midwinter immediately before a cold rain to reduce volatility and enhance weed suppression.
Remarks Weigh and distribute uniformly and exactly over precisely measured areas to ensure accurate applications. Oregon results over 9 years suggest perennial weeds can be suppressed with 4-, 3-, and 2-lb ai/A rates applied in 3 consecutive years. Grazing livestock is prohibited. Inhibits cellulose and cell wall formation.
Site of action Group 20: inhibits cell wall synthesis Site A
Chemical family Nitrile
dimethenamid-p (Freehand or Tower)
Rate 100 to 200 lbs product/A depending on species present
Time Apply to established plantings prior to weed emergence.
Remarks Does not control emerged weeds. Wait 2 to 4 weeks for soil to settle before application. Irrigation or rainfall is needed to activate herbicide. Consult label for tolerant species.
Caution Do not apply to seedbeds.
Site of action Group 15: inhibits very long chain fatty acid synthesis
Chemical family Chloroacetamide
dithiopyr (Dimension 2EW)
Rate 0.375 to 0.5 lb ai/A (0.75 to 1 quarts/A)
Time Apply preemergence around bases of ornamental plants in landscape.
Remarks For best results, prepare a weed-free surface with minimal clods and leaf debris.
Caution Do not exceed 1.5 fl oz/1,000 sq ft every 3 to 4 months, or 4.5 fl oz/1,000 sq ft per year. Do not apply to plant roots or weakened ornamental plants, or when drift potential is moderate to high. Do not use in enclosed structures. Dithiopyr is toxic to fish and highly toxic to oysters, shrimp, and other aquatic organisms.
Site of action Group 3: microtubule assembly inhibitor
Chemical family Pyridine
EPTC (Eptam 7E)
Rate 5 to 14.9 lb ai/A (5.75 to 17 pints/A) depending on target species
Time Apply and immediately incorporate 2 to 3 inches deep with a rototiller 2 weeks before transplanting balled or canned stock; or, spray postplant and incorporate with tillage. In spring, apply around established plants after growth and incorporate.
Remarks Use higher rates for perennial weed control and incorporate to a depth of 6 inches with a rototiller. Note sensitive flowers listed on label. Primarily for grass control including quackgrass suppression. Inhibits shoot growth.
Site of action Group 8: lipid synthesis inhibitor but not an ACCase inhibitor
Chemical family Thiocarbamate
flumioxazin (Broadstar 0.25G)
Rate 0.375 lb ai/A (150 lb/A Broadstar)
Time Apply to weed-free surface.
Caution Foliage of desirable crops must be dry at the time of application. Wet foliage will trap granules on the leaf surface and burn the foliage.
Site of action Group 14: protoporphyrinogen oxidase inhibitor
Chemical family N-phenylphthalimide
halosulfuron-methyl (Sedgehammer)
Nutsedge control in landscapes
Rate 0.031 to 0.062 lb ai/A (2/3 to 1 1/3 oz product/A)
Time After nutsedge has reached the 3- to 8- leaf stage of growth.
Remarks Allow 3 months after transplanting ornamentals before application. A second treatment may be required 6 to 10 weeks later. Do not exceed 0.25 lb ai/A total or four applications per season. Use 0.5% nonionic surfactant concentration for broadcast applications.
Caution Do not apply as an over-the-top spray to desirable flowers, ornamentals, vegetables, shrubs or trees. Apply to actively growing nutsedge that is not stressed.
Site of action Group 2: acetolactate synthase (ALS) inhibitor
Chemical family Sulfonylurea
isoxaben (Gallery 75 DF)
Rate 0.495 to 0.998 lb ai/A (0.66 to 1.33 lb/A)
Time Apply late summer to early fall, in early spring, or immediately after cultivation. Apply to debris-free soil surface.
Remarks Identify weeds; adjust rates according to charts on label. Activate with 0.5 inch water or shallow cultivation before weeds emerge. Chemical stability remains adequate when left on soil surface for 21 days. Primarily controls broadleaf weeds.
Caution Do not apply to newly transplanted crops until media settle. See label for 14 sensitive ornamental species for which isoxaben is not recommended, including hydrangea, purple coneflower, and yucca. Use untreated soil to fill around transplants if isoxaben has been applied within 1 year.
Site of action Group 21: inhibits cell wall synthesis Site B
Chemical family Benzamide
indaziflam (Spect(i)cle 20 WSP)
Rate 0.047 to 0.063 lb ai/A (3.75 to 5 oz/A Specticle)
Time Apply prior to weed seed germination, in fall to early spring, to firmed soil that does not have cracks.
Remarks Existing vegetation must be controlled with glyphosate or burndown herbicides such as glufosinate or paraquat. Controls annual broadleaf and grass weeds and perennial weeds from seed only. Existing perennial/biennial weeds growing from roots will not be controlled. Rainfall or irrigation of ¼ inch or more within 3 weeks of application is required for maximum efficacy.
Caution Read label thoroughly to understand situations that should be avoided. This product has a long residual.
- Avoid direct contact with foliage, green bark, or roots of desired species. Clean spray tanks thoroughly after use.
- Do not apply around bedding plants.
- Do not apply around bearing fruit trees, unless beyond the tree dripline.
- Applications over heavily mulched areas may not control weeds adequately. It is best to apply before the mulch is applied.
- Avoid applications to newly seeded grasses.
- Surface and groundwater advisories are included on the label because of potential harm to non-target organisms and potential for runoff and percolation to ground water.
Site of action Group 29: inhibits cellulose biosynthesis
Chemical family Alkylazine
napropamide (Devrinol 2G)
Rate 4 to 6 lb ai/A (200 to 300 lb/A)
Time Apply any time to weed-free soil, then sprinkler irrigate to wet soil 1 to 2 inches deep, or apply during midwinter rains in western Oregon for annual weed control.
Remarks Use higher rates with severe weed populations or when broadleaf weeds are present. Primarily grass control Inhibits root growth.
Site of action Group 15: inhibits very long chain fatty acid synthesis
Chemical family Acetamide
oryzalin (Surflan AS)
Rate 2 to 4 lb ai/A (2 to 4 quarts/A) depending on length of control
Time Apply any time to weed-free soil, then sprinkler irrigate with 0.5 inch if no rain falls within 1 week, or cultivate 1 inch deep to activate herbicide for annual weed control.
Remarks Consult label for tolerant ornamental species. Primarily grass control. Inhibits mitosis, primarily in roots.
Site of action Group 3: microtubule assembly inhibitor
Chemical family Dinitroaniline
oxadiazon (Ronstar 2G)
Rate 2 to 4 lb ai/A (100 to 200 lb/A) depending on target weed species
Time Apply any time to weed-free soil and irrigate with 0.25 to 0.33 inch water immediately after applying for annual weed control.
Remarks Do not cover with soil or mulch, or incorporate, because weed control will desist. Weeds in the pink family (chickweed, mouseear chickweed, and pearlwort) are resistant. Primarily broadleaf control (controls weed seedlings by contact action during emergence.)
Caution See label for sensitive ornamentals, which include varieties of rhododendron, spruce, hemlock, azalea, viburnum, and cotoneaster. Avoid contaminating water intended for irrigation. Do not use on plants that will produce fruit within 1 year.
Site of action Group 14: protoporphyrinogen oxidase inhibitor
Chemical family Oxadiazole
pendimethalin (Pendulum 2G)
Rate 2 to 4 lb ai/A (100 to 200 lb/A Pendulum 2G) depending on desired length of weed control
Time Apply at time of planting or before weed seed germinates.
Remarks Primarily for grass control. Soil should be loose and free from all established weeds. Water within a few days to activate herbicide before weeds emerge. Inhibits mitosis in roots and shoots.
Caution Granules may stain stone, wood, or other porous surfaces.
Site of action Group 3: microtubule assembly inhibitor
Chemical family Dinitroaniline
prodiamine (Barricade 65WG or Endurance)
Rate 0.65 to 1.5 lb ai/A (1 to 2.3 lb/A) depending on desired length of weed control
Time Apply any time to weed-free soil, and incorporate with 0.5 inch water or rain within 14 days.
Remarks May be applied to newly transplanted and established ornamentals as a broadcast, over-the-top spray. Activate with 0.5 inch of rain or irrigation water, or with shallow incorporation. Inhibits germination and root development.
Caution Do not exceed 2.3 lb/A in any 12-month period.
Site of action Group 3: microtubule inhibitor
Chemical family Dinitroaniline
pronamide (Kerb)
Rate 1 to 2 lb ai/A (2 to 4 lbs product/A)
Time Apply in fall before soil freezes.
Remarks For use on woody perennials. Requires soil moisture from rain or irrigation to activate; do not incorporate mechanically. Use lower rates for annual grasses and light-texture soils; higher rates for perennial grasses and heavier soils. Control of established grasses is slow. Degraded by microorganisms in warmer weather. Inhibits root growth.
Caution A restricted-use pesticide.
Site of action Group 3: microtubule assembly inhibitor
Chemical family Benzamide
S-metolachlor (Pennant Magnum)
Rate 1.24 to 2.48 lb ai/A (1.3 to 2.6 pints/A)
Time Apply as direct spray toward base of desired plant, either to established ornamentals or 5 days after transplanting.
Remarks Existing weeds must be removed. Primarily targets grasses, but controls some broadleaf weeds and suppresses nutsedge. Inhibits seedling roots and/or shoots.
Caution Do not apply more than twice per year. Consult label for tolerant ornamentals.
Site of action Group 15: inhibits very long chain fatty acid synthesis
Chemical family Chloroacetamide
ESTABLISHED LANDSCAPES—Convenient Soil-applied Premixes for Broad-spectrum Control of Grasses and Broadleaf Weeds
benefin + oryzalin (XL 2G)
Rate 200 lb/A per application with at least 2 months between applications; do not exceed 800 lb/A per year
Time Apply before target weeds germinate.
Remarks Precisely calibrate application equipment, preferably at half rates, to enable two perpendicular passes for increased accuracy. Inhibits cell division or mitosis, primarily in roots.
Caution Sensitive species include Douglas-fir, eastern hemlock, and begonia.
Site of action (both) Group 3: microtubule assembly inhibitor
Chemical family (both) dinitroaniline
isoxaben + trifluralin (Snapshot 2.5TG)
Rate 200 lb/A
Time Apply to soil that is free from weeds and debris. Soil must be settled with water and free of cracks after transplanting.
Remarks Activate within 31 days using 0.5 inch of water or shallow cultivation before weeds begin to emerge. Follow label instructions for repeat treatments.
Caution Do not apply to unrooted liners or cuttings, bedding plants, or new-planted ground covers.
Site of action (isoxaben) Group 21: inhibits cell wall synthesis Site B; (trifluralin) Group 3: microtubule assembly inhibitor
Chemical family (isoxaben) benzamide; (trifluralin) dinitroaniline
oxadiazon + prodiamine (RegalStar G)
Rate 200 lb/A
Time Any time during the year, but before weed seeds germinate.
Remarks Cultivating or disturbing the soil after application diminishes weed control. Controls spotted spurge, knotweed, yellow woodsorrel, and clover.
Caution Do not apply herbicide granules to wet foliage. Cultivars of Ilex spp. (holly) and Rhododendron spp. may be sensitive to this product.
Site of action (oxadiazon) Group 14: protoporphyrinogen oxidase inhibitor; (prodiamine) Group 3: microtubule assembly inhibitor
Chemical family (oxadiazon) oxadiazole; (prodiamine) dinitroaniline
oxyfluorfen + oryzalin (Rout)
Rate 50 to 100 lb/A (2% + 1% formulation, respectively)
Time Apply uniformly, either in spring before weed seed germination and crop growth flush, or to weed-free soil.
Remarks Requires 0.5 inch water immediately after application to activate and to wash product from leaves. Acts as contact-type herbicide and inhibits cell division or mitosis in roots and shoots, respectively.
Caution Do not apply to wet foliage or plants with whorls. Note all other precautions on label.
Site of action (oxyfluorfen) Group 14: protoporphyrinogen oxidase inhibitor; (oryzalin) Group 3: microtubule assembly inhibitor
Chemical family (oxyfluorfen) diphenylether; (oryzalin) dinitroaniline
ESTABLISHED LANDSCAPES—Postemergence or Foliar Applied
clethodim (Prism: registered only in Oregon; or Envoy)
Rate Consult labels
Time Apply postemergence to actively growing annual or perennial grasses as listed on label.
Remarks Consider environmental and plant growth conditions that affect leaf uptake (see label for guidelines). Controls annual bluegrass.
Caution Do not exceed 68 fl oz/A per season.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family Cyclohexanedione
clove leaf oil (Matran EC)
Rate 5 to 8% dilution in 25 to 100 gal of water, depending on weed size, temperature, and sunlight intensity.
Time Before weeds are 6 inches tall.
Remarks OMRI-listed and WSDA-approved herbicide for in-crop use. Apply before crop emergence, or between rows after emergence, avoiding contact with desirable foliage. Directed sprays or hooded sprayers are recommended. Works best on annual weeds less than 6 inches. Performance may be erratic depending on environmental conditions. Bright sunlight improves efficacy. No preharvest interval or reentry interval.
Caution Use appropriate nozzles to prevent drift onto desirable foliage.
fenoxaprop ethyl (Acclaim Extra)
Rate 13 to 39 fl oz/A or /1,000 sq ft
Time Apply to actively growing perennial and annual grasses
Remarks Adjust rates depending on number of grass tillers (see label). Ensure thorough coverage to actively growing, susceptible grasses. Repeat after grass begins active growth, but do not exceed 120 fl oz/A per season. Inhibits fatty acid production, cell membranes, and new growth.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family Aryloxyphenoxy propionate
fluazifop (Fusilade II or Ornamec)
Rate Consult labels
Time Apply to actively growing grasses, or within 7 days after irrigation, as a directed spray with 0.25% nonionic surfactant when susceptible grasses are in the labeled growth stage.
Remarks Identify grasses, and adjust rates depending on susceptibility and stage of weed growth as label instructs. Results often are erratic if grasses are stressed from lack of vigor, drought, high temperature, or low fertility. More mature grasses and quackgrass can be controlled but may require two applications. Annual bluegrass and all fine fescues resist treatment. Inhibits fatty acid production, cell membranes, and new growth.
Caution Do not tank mix with other pesticides. Do not apply within 5 days of other pesticide treatments.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family Aryloxyphenoxy propionate
glufosinate ammonium (Finale)
Spot or directed spray only
Rate Consult label
Time Apply to thoroughly cover actively growing weeds. Avoid all contact with desirable foliage and green bark.
Remarks To trim or edge landscape plantings.
Site of action Group 10: glutamine synthase inhibitor
Chemical family Phosphinic acid
glyphosate (numerous product names)
Not for ground covers
Rate Spray: 1.5 to 5 lb ai/A or 1 to 2% solution for high-volume sprayers
Time Apply as directed spray toward base of bush, when weeds are actively growing or moving sugars to roots.
Remarks Use lower rates for annual weeds; consult label for higher rates and time of application for perennial weeds. Expedite Application Equipment contains a special formulation using small-droplet technology. Inhibits production of three amino acids and protein synthesis.
Caution Do not spray green foliage or green bark. If applications are repeated, do not exceed a total of 10.6 lb ai/A (10.6 quarts/A) per year. Repeated use in Australian orchards for several years has resulted in resistant biotypes. To avoid developing weed resistance, rotate chemicals and weed control practices.
Site of action Group 9: inhibits EPSP synthase
Chemical family None generally accepted
glyphosate (several products)
Not for ground covers
Rate Wiper: use 33% solution
Time Apply 1 gal product to 2 gal water and wipe weeds. Avoid contact with desirable vegetation.
Remarks In severe infestations, reduce equipment ground speed or apply in two directions to ensure contact with wiper. (See remarks above.)
Site of action Group 9: inhibits EPSP synthase
Chemical family None generally accepted
halosulfuron-methyl (Sedgehammer)
Rate 0.031 to 0.062 lb ai/A (0.66 to 0.33 oz/A) to three- to eight-leaf nutsedge
Time Post-directed spray on established woody ornamentals
Remarks For control of nutsedge. Use lower rate on light infestations and high rate on heavy infestations. Do not exceed 5.33 oz/A or four applications per year. Add a nonionic surfactant at 0.25 to 0.5% v/v. May tank-mix with glyphosate.
Caution Do not apply over the top of desirable flowers, ornamentals, vegetables, trees, or shrubs.
Site of action Group 2: acetolactate synthase (ALS) inhibitor
Chemical family Sulfonylurea
lemongrass oil (Green Match EX)
Rate 7 to 15% dilution depending on weed size and species.
Time When weeds are less than 6 inches tall.
Remarks OMRI-listed, NOP-compliant, and WSDA-approved organic burndown herbicide for use in crop and non-crop sites. Green Match damages foliage on contact; leaf damage is visible within hours. Directed sprays or hooded sprayers are recommended. Coverage is very important. Cool weather may slow activity. No reentry interval. Fast wilting or necrosis of leaves due to removal of waxy cuticle.
Caution Use appropriate nozzles to prevent drift onto desirable foliage.
pelargonic acid (Scythe)
Rate Broadcast: use 5 to 10 gal product per 100 gal water. Spot spray: use 5 to 10% solution (6.67 to 13 fl oz/gal) to cover 400 sq ft.
Time Apply to thoroughly wet foliage, either broadcast to non-crop area or preemergence to ornamental crop; or spot treat and trim around ornamentals, trees, flower beds, paths, and drives.
Remarks Controls small, actively growing weeds and weakens established weeds by removing susceptible vegetation. Disrupts cell membranes, causing leakage and symptoms of leaf burn.
Site of action Group 26: unknown
Chemical family Carboxylic acid
sethoxydim (Segment)
Crops listed on label
Rate 0.28 to 0.47 lb ai/A (36 to 60 fl oz/A)
Time Apply at optimum growth stage of grasses listed on the label.
Remarks Identify susceptible grasses. Control often is erratic on grasses stunted or stressed from drought, high temperatures, or low fertility. Resistant grasses include annual bluegrass and all fine fescues. Quackgrass can be suppressed. Inhibits fatty acid production, cell, membranes, and new growth.
Site of action Group 1: acetyl CoA carboxylase (ACCase) inhibitor
Chemical family Cyclohexanedione
ESTABLISHED LANDSCAPES—Trees, Shrubs, Roses, and Ground Covers—Root Growth Control
spunbonded polypropylene + trifluralin (Biobarrier)
Rate Consult label
Remarks A geo-textile fabric containing permanently attached nodules of time-release herbicide. Prevents root encroachment when placed vertically, horizontally, or surrounding structures such as sidewalks, roads, building foundations, curbs, tennis courts, swimming pools, septic fields, or underground pipes or cables in the soil. Extend edge of fabric 18 inches beyond structure to prevent root growth around edges of protected structure. Maintain at least 4 inches of soil overlay. Physical and mitotic inhibition of roots.
Site of action (trifluralin) Group 3: microtubule assembly inhibitor
Chemical family (trifluralin) dinitroaniline