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Pest SolutionsPESTS + WEEDSUSING PESTICIDES OR HERBICIDES?
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Grassy Weeds in Lawns
Many species
Updated Mar 17, 2023
Make a Positive Identification
- Common grassy weeds (grow from base and have parallel leaf veins) include crabgrass, annual bluegrass, creeping bentgrass, and quackgrass.
- Find quick tips for identification and control of each grassy weed species in lawns.
Crabgrass
Species: Crabgrass
Yesim Sahin, iStock
Smooth Crabrass (Digitaria ischaemum) Large crabgrass (D. sanguinalis)
- Two species of crabgrass (smooth and large) are common weeds in lawns, landscapes, and patios.
- Crabgrass stands out in lawns. It has a different color and texture from lawn grasses. It doesn’t mix with other grasses in lawns as shown in the photo.
- Crabgrass spreads quickly by seed. It takes over neglected lawns and other areas during the summer growing season.
Species: Crabgrass
Photo credits
Left:
Rebekah D. Wallace, University of Georgia, Bugwood.org (cropped)
Right:
Lynn Sosnoskie, University of Georgia, Bugwood.org (cropped)
Crabgrass Life Cycle
- Crabgrass is a warm season annual grass (completes life cycle in a single growing season).
- Seeds sprout in the mid-to-late spring when soils are warm. New plants continue to sprout and grow throughout the summer.
- Crabgrass flowers in July and August. The flowers of crabgrass are long and finger-like (left photo).
- A single large crabgrass plant produces 100,000 or more seeds (right photo). The seeds remain viable in the soil for at least 3 years.
- Plants die each year with the first frost in the fall.
Species: Crabgrass
Joseph M. DiTomaso, University of California - Davis, Bugwood.org
Tips to Get Rid of Crabgrass in Lawns
- Physically remove young crabgrass plants in the late spring.
- The photo shows large crabgrass (right), smooth crabgrass (left), and seedlings growing together. Crabgrass is easiest to remove at this stage before its deep root system establishes.
- Keep crabgrass from going to seed, if possible.
- Lawn-specific herbicides (weed killers) with the active ingredient quinclorac kill crabgrass without damaging lawns when used according to the directions.
- Herbicides that kill germinating seedlings (preemergent) also work. They need to be applied several weeks before crabgrass seeds will germinate.
- Successful crabgrass control requires several years of monitoring and treatment.
Annual Bluegrass
Species: Annual Bluegrass
Ian_Redding, iStock
Annual Bluegrass (Poa annua)
- Annual bluegrass is a common, grassy weed in lawns, landscapes, and patios.
- It completes its life cycle in a single growing season (annual) or remains growing after one year (perennial).
- It spreads quickly by seed.
- Annual bluegrass may become seasonally dominant in lawns and disturbed areas.
Species: Annual Bluegrass
Photo credits
Left:
Shawn Wright, University of Kentucky, Bugwood.org (cropped)
Right:
"Poa annua flowerhead NC2" by Harry Rose is licensed under CC BY 2.0 (cropped).
Annual Bluegrass Life Cycle
- Shallow-rooted grasses grow in a small clump. They grow year-round in mild summer locations.
- Annual bluegrass seeds germinate throughout late fall and winter.
- Flowers (right photo) form in the early spring and other times of the year.
- Individual annual bluegrass plants may produce dozens to hundreds of seeds even when the plants are mowed.
Species: Annual Bluegrass
"Poa annua plant NC2" by Harry Rose is licensed under CC BY 2.0.
Tips to Get Rid of Annual Bluegrass in Lawns
- Individual plants and small patches of annual bluegrass can be pulled or removed with tools. Plants are shallow-rooted and easy to remove.
- Herbicide products that contain active ingredients glyphosate and herbicides which target grasses (grass-selective) are effective treatments for annual bluegrass when label directions are followed. These herbicides will also damage lawn grasses. Follow up by reseeding sprayed areas.
- Herbicides that kill germinating seedlings (preemergent) also work. They need to be applied before annual bluegrass seeds germinate.
- Requires several years of monitoring and treatment.
Creeping Bentgrass
Species: Creeping Bentgrass
Weston Miller, Oregon State University
Creeping Bentgrass (Agrostis stolonifera)
- Creeping bentgrass is a mat-forming grass that spreads with seeds and above ground stems (stolons). The photo shows light-colored bentgrass spreading in a lawn.
- This perennial grass (lives many years) prefers cool, moist regions.
- Plants grow less than 6 inches tall.
- Creeping bentgrass outcompetes other lawn grasses in compacted soils with low fertility.
- Creeping bentgrass is a preferred grass species for golf courses and specialty lawns.
Species: Creeping Bentgrass
Photo credits
Left:
"Creeping bentgrass" by Tony Frates is licensed under CC BY-NC-SA 2.0 (cropped).
Right:
"Agrostis stolonifera" by Matt Lavin is licensed under CC BY-SA 2.0 (cropped).
Creeping Bentgrass Life Cycle
- Stems grow horizontally along the ground surface up to 40 inches. Mature leaves are light green and 0.5–5 inches long and narrow (no more than 0.4 inches wide).
- Flowers grow 0.5–6 inches long in a loose cluster as shown in the photo (right). Flowers appear from early summer through early fall. Creeping bentgrass produces many very small seeds per plant. Seeds are viable for up to 4 years. Seeds are spread by wind, water flow, and on animals.
Species: Creeping Bentgrass
OSU Turfgrass Management Program
Tips to Get Rid of Creeping Bentgrass in Lawns
- Determine whether you can live with bentgrass in your lawn. If not, you’ll want to fertilize your lawn and reseed with desired grasses (perennial ryegrass and/or fescues).
- Dig out small patches. Remove shallow roots and all stolons. Apply grass seed or lawn patch product to exposed soil.
- Herbicide products containing active ingredients glyphosate and herbicides that target grasses (grass-selective) are effective treatments for creeping bentgrass when label directions are followed. These herbicides will also damage lawn grasses. Follow up by reseeding treated areas.
- Glyphosate-resistant varieties of creeping bentgrass have been grown in the Pacific Northwest.
Quackgrass
Species: Quackgrass
ioanna_alexa, iStock
Quackgrass (Elymus repens)
- Quackgrass is a common, invasive perennial (lives many years) grass.
- It thrives in agricultural and moist sites with disturbed soil. It grows in farm fields, gardens, lawns, moist meadows, roadsides, irrigation canals, drainage ditches, and along creeks and rivers.
- It grows up to 4 feet tall and forms dense patches.
- In lawns, quackgrass outcompetes desired grasses. Its color and texture stand out in high-maintenance lawns.
Species: Quackgrass
Photo credits
Left:
Steve Dewey, Utah State University, Bugwood.org (cropped)
Right:
Steve Dewey, Utah State University, Bugwood.org (cropped)
Quackgrass Life Cycle
- Quackgrass grows year-round in mild winter areas. The perennial grass spreads by seeds and roots to form dense stands.
- Flowers grow on a 2- to 10-inch long, flattened spike (right photo). Flowers appear from late spring through summer and produce a few dozen seeds per plant. Seeds are viable for 1-6 years.
- Once seedlings establish, root structures (rhizomes) spread to increase the size of the patch (right photo.
Species: Quackgrass
Juta.lopp, CC BY-SA 3.0, via Wikimedia Commons
Tips to Get Rid of Quackgrass in Lawns
- Determine whether you can live with quackgrass in your lawn.
- Dig out small patches. Remove all the roots as shown in photo.
- Herbicide products that contain active ingredients glyphosate and herbicides which target grasses (grass-selective) are effective treatments for creeping quackgrass when label directions are followed. These herbicides will also damage lawn grasses. Follow up by reseeding treated areas.
Look-Alikes: Nutsedge & Horsetail
Species: Nutsedge
Photo credits
Left:
User:Blahedo, CC BY-SA 2.5, via Wikimedia Commons (cropped)
Right:
"File:Yellow Nutsedge Cyperus esculentus (43998391481).jpg" by Homer Edward Price is licensed under CC BY 2.0 (cropped).
Nutsedge (Cyperus esculentus & C. rotundus)
- Nutsedge is a spreading, perennial plant that resembles grass.
- In the Pacific Northwest, nutsedges are weeds in yards, gardens, and agriculture.
- Nutsedge leaves are stiffer than lawn grass, and arranged in sets of three. They grow from a triangular base (right photo).
- Nutsedge spreads aggressively via underground tubers and sometimes by seed.
- Nutsedge takes over lawn areas. It doesn’t mix with grasses when mowed.
Different risks or methods
- Avoid bringing nutsedge onto your property via contaminated compost or on tools.
- Take action to remove nutsedge. Keep it from establishing. It requires several years of effort and monitoring to get rid of a patch of nutsedge.
Species: Horestail / Scouring Rush
Steve Dewey, Utah State University, Bugwood.org
Horsetail / Scouring Rush (Equisetum spp.)
- Horsetail is native and grows throughout the Pacific Northwest. The photo shows several different species of Equisetum.
- Plants live for many years and are often found in wet or seasonal wet areas.
- Uncontrolled horsetail growth degrades desirable lawns and landscape plantings.
- It stands out in lawns and doesn’t blend in with grasses when mowed.
Different risks or methods
- Horsetail is a native plant that thrives in a variety of habitats. It dominates in wet and sunny locations.
- For lawns, remove horsetail stems throughout the year.
Grassy Weeds in Lawns Benefits
- Grassy weeds cover soil in low-maintenance lawns and neglected areas.
- They are pioneer plants that grow in compacted soil with low fertility.
- Grassy weeds readily spread on their own.
Grassy Weeds in Lawns Risks
- Plants stand out and make lawns rough and uneven. Grassy weeds often dominate neglected areas.
- Grassy weeds are difficult to control. They require ongoing action and monitoring.
Risk Card
Does it cause harm?
Adults & Children
None
Property
Some
Cosmetic damage to lawn
Pets
None
Annoyance
Some
Depends on preference
Environment
None
Action Optional
For high maintenance lawns, consider taking action.
Take Action?
Grassy weeds in lawns and neglected areas are common. People have different opinions about them.
Do I need to take action?
- Action for grassy weeds in lawns is optional.
- Determine whether you will leave them alone or you want to take action.
What if I do nothing?
Grassy weeds spread rapidly. They take over lawns and neglected areas.
Prevent Grassy Weeds in Lawns
Yarygin, iStock
Grow a Dense Lawn
- A healthy lawn shades weed seeds and keeps them from growing.
- Apply grass seed over existing lawns (overseed) where grass is sparse. Overseed every year or as needed to maintain thick grasses in your lawn.
- Apply fertilizer and water to grow robust grasses.
Weston Miller, Oregon State University
Use Lawn Patch Products or Apply Seed to Bare Spots
- Weed seeds sprout and take root in bare soil. Cover bare spots with lawn patch products. They combine seed, fertilizer, and mulch.
- Or sprinkle lawn seed on bare spots.
- Irrigate the area as needed to germinate the seeds.
Maintain a Healthy Lawn
- Maintain the right growing conditions needed for strong, healthy lawn grasses. Healthy lawns resist weeds.
- Lawns change over time. After lawn seed has been sowed or sod laid, a mixture of desired lawn grasses and broadleaf weeds, grassy weeds, and moss will evolve.
- Soil drainage, soil fertility, sunlight, water stress, and how the lawn is cared for and used will affect how your lawn looks over time.
- Set realistic expectations for your lawn. Match the lawn standards you want to maintain with the right maintenance schedule.
- If the quality of your lawn doesn’t match your standards, consider a lawn renovation.
- For more information, see Prevent Lawn Problems.
Solutions for Grassy Weeds in Lawns
- Prevent lawn weed problems by maintaining a healthy lawn. A thick, robust lawn keeps weeds from growing. See Prevent Lawn Problems for details.
- Digging individual plants out by the root is effective. Quackgrass and annual bluegrass won’t regrow if you remove plants by the roots. Bentgrass and quackgrass have spreading root systems and require more work to remove all of the plant.
- Weed killers (herbicides) effectively control grassy weeds in lawns when used according to the label instructions. Follow up by reseeding the treated area.
- More weeds will grow in the same spot unless you take the steps to prevent them.
- For lawns with many grassy (and broadleaf) weeds, consider a lawn renovation. See Practical Lawn Establishment and Renovation (OSU Extension Service) for details.
NEED HELP?
Consider a licensed pest control company. Learn How to Hire a Pest Control Company.
Your local Extension Specialist in Oregon and other states can suggest other methods.
Jump to
| Method | Does it work? | Is it safe? | Recommendation |
|---|---|---|---|
A Maintain a Healthy Lawn |
Very effective |
Low risk |
Recommended |
B Physically Remove Plants |
Very effective |
Low risk |
Recommended |
C Postemergent Herbicides for Weedy Grasses in Lawns |
Effective |
Moderate risk |
Use if Necessary |
D Quinclorac Herbicide for Crabgrass in Lawns |
Effective |
Moderate risk |
Use if Necessary |
E Preemergent Herbicides for Crabgrass & Annual Bluegrass in Lawns |
Somewhat effective |
Moderate risk |
Use if Necessary |
|
F If Using Herbicides, Protect Yourself & Minimize Risks
|
A
Maintain a Healthy Lawn
Non-Chemical Method
OSU Turfgrass Management Program
Maintain a Healthy Lawn
Recommended
You can minimize weeds growing in your lawn by growing healthy, robust grasses.
| Does it work? | Very effective Use preventive measures for best results. |
| How much effort? | High effort Maintaining a healthy lawn requires planning and ongoing effort. |
| What's the risk? | Low risk |
| Possible risk of exposure or harm from chemicals | NONE |
The best defense against weed problems in your lawn is to maintain a healthy lawn.
B
Physically Remove Plants
Non-Chemical Method
PICSUNV, iStock
Physically Remove Plants
Recommended
Learn to recognize the grassy weeds you can’t tolerate in your lawn. Find seedlings and young plants and remove them as needed.
| Does it work? | Very effective
|
| How much effort? | Moderate effort Remove small patches of weedy grasses as needed. Bigger patches will require more work. |
| What's the risk? | Low risk |
| Possible risk of exposure or harm from chemicals | NONE |
Each type of weedy grass requires a specific method to physically remove the plant.
Weston Miller, Oregon State University
"Poa annua plant NC2" by Harry Rose is licensed under CC BY 2.0.
Weston Miller, Oregon State University
Juta.lopp, CC BY-SA 3.0, via Wikimedia Commons
C
Postemergent Herbicides for Weedy Grasses in Lawns
Chemical Method: Use with caution
Weston Miller, Oregon State University
Postemergent Herbicides for Weedy Grasses in Lawns
Use if Necessary
- Herbicide products that contain active ingredients glyphosate and herbicides which target grasses (grass-selective) are effective treatments for weedy grasses in lawns when label directions are followed.
- These postemergent herbicides are used to kill weeds after they sprout and grow.
- Follow up by reseeding areas where you have used herbicide to fill in gaps.
| Does it work? | Effective
|
| How much effort? | Moderate effort Spot-spray grassy weeds as needed or consider a total lawn renovation. Reseed the area with desired lawn grasses. |
| What's the risk? | Moderate risk
|
| Possible risk of exposure or harm from chemicals | El uso de herbicidas conlleva cierto grado de riesgo. El riesgo más bajo se presenta con el uso de métodos alternativos. You may be exposed to an herbicide if you:
Follow directions closely to reduce risk. |
Glyphosate and grass-selective herbicides such as fluazifop used individually or in a mixture are effective chemical treatments for grassy weeds. Look for these chemical names in the “Active Ingredients” section of product labels.
Weston Miller, Oregon State University
Weston Miller, Oregon State University
Herbicide Application Tips FOR GRASSY WEEDS
- Premixed products are available in stores.
- Read and understand the DIRECTIONS FOR USE section of the product label before reseeding or replanting the treated area.
- Reseed the spot-treated areas with grass seed or lawn patch.
- If there are many weeds, consider a total lawn replacement. See Practical Lawn Establishment and Renovation (OSU Extension Service) for details.
Herbicide Application Tips for Crabgrass and Annual Bluegrass
- For annual grassy weeds such as crabgrass and annual bluegrass, for best results treat before the plants flower.
- Treating annual grassy weeds after plants flower won’t keep new seeds from sprouting and growing.
- Seeds in the soil will likely sprout in future years.
Herbicide Application Tips for Quackgrass and Creeping Bentgrass
- Killing rhizomes is critical to eliminate quackgrass and control creeping bentgrass.
- Herbicide products applied to the leaves during the spring or fall are effective at controlling spreading grasses.
- Herbicides applied after flowering are more effective at killing rhizomes.
- However, the specific timing and application method depends on the herbicide product. Follow the label instructions for best results.
- It takes repeated effort over several years to get rid of a well-established stand of quackgrass and creeping bentgrass.
D
Quinclorac Herbicide for Crabgrass in Lawns
Chemical Method: Use with caution
Weston Miller, Oregon State University
Quinclorac Herbicide for Crabgrass in Lawns
Use if Necessary
- Certain herbicide products with the active active ingredient quinclorac control crabgrass. The example product label states “CRABGRASS KILLER.”
- Quinclorac is a postemergent herbicide used to kill crabgrass after it sprouts and grows.
| Does it work? | Effective
|
| How much effort? | Moderate effort Spot-spray grassy weeds as needed or consider total lawn renewal. Reseed the area with desired lawn grasses. |
| What's the risk? | Moderate risk
|
| Possible risk of exposure or harm from chemicals | El uso de herbicidas conlleva cierto grado de riesgo. El riesgo más bajo se presenta con el uso de métodos alternativos. You may be exposed to an herbicide if you:
Follow directions closely to reduce risk. |
The active ingredient quinclorac selectively controls crabgrass plants. Look for this chemical name in the “Active Ingredients” section of product labels.
Quinclorac Application Tips
- Spray individual plants in lawns that contain few crabgrass plants when hand removal is not an option.
- For lawns containing many crabgrass plants, consider applying quinclorac over the entire lawn. This application will kill most of the crabgrass in the treated area.
- Read and understand the DIRECTIONS FOR USE section of the product label before reseeding or replanting the treated area.
- Reseed the spot-treated areas with grass seed or lawn patch.
- If there are many weeds, consider a total lawn replacement. See Practical Lawn Establishment and Renovation (OSU Extension Service) for details.
E
Preemergent Herbicides for Crabgrass & Annual Bluegrass in Lawns
Chemical Method: Use with caution
Lynn Sosnoskie, University of Georgia, Bugwood.org
Preemergent Herbicides for Crabgrass & Annual Bluegrass in Lawns
Use if Necessary
- Preemergent herbicides work to control seeds (such as the ones shown in the photo) in the soil before they sprout and grow.
- They are intended for use on annual weeds, such as crabgrass and annual bluegrass.
- They don’t work to kill weedy grasses (and broadleaf weeds) that have already emerged.
| Does it work? | Somewhat effective The effectiveness of preemergent herbicides depends on timing the application several weeks before weed seeds will germinate. |
| How much effort? | Moderate effort Research and select the product. Read label instructions and safety information. Apply herbicide. Re-apply preemergent herbicides as needed. |
| What's the risk? | Moderate risk
|
| Possible risk of exposure or harm from chemicals | El uso de herbicidas conlleva cierto grado de riesgo. El riesgo más bajo se presenta con el uso de métodos alternativos. You may be exposed to an herbicide if you:
Follow directions closely to reduce risk. |
- For best results, look for preemergent herbicide products that are specifically for use in lawns. There are numerous active ingredients that work.
- Look for products with labels that state “crabgrass preventer” and “grassy weed preventer.”
APPLICATION tips for Preemergent Herbicides for Grassy Weeds
Application Tips for Preemergent Herbicides for Annual Bluegrass
- Annual bluegrass seeds germinate in the late summer or early fall when soil temperatures begin to cool. Seeds sprout when the soil temperature drops below 70°F.
- The best time to apply preemergent herbicides to control annual bluegrass seeds is several weeks before seeds will germinate.
- Repeat applications may be needed.
Application Tips for Preemergent Herbicides for Crabgrass
- Crabgrass seeds germinate in the mid-to-late spring when soil temperatures begin to warm.
- The best time to apply preemergent herbicides to control crabgrass seeds is several weeks before seeds will germinate. Crabgrass seeds sprout in the spring when soils warm to 50°F to 55°F for at least 3 days in a row.
- Repeat applications may be needed.
Consider Hiring a Lawn Care Professional
- Successfully using preemergent herbicides to kill crabgrass and annual bluegrass seeds requires careful timing and understanding of weed biology.
- If getting rid of these weeds in your lawn is important to you, consider hiring a professional. They have the knowledge and skills to get the job done right. They also have access to additional herbicide ingredients beyond what you can find in stores.
If Using Herbicides, Protect Yourself & Minimize Risks
Chemical Method: Use with Caution
FangXiaNuo, iStock
Why is it important to ready herbicide labels?
- They have detailed information on how to use the product correctly and legally.
- They contain information on potential hazards of the product.
- They provide instructions you should follow for poisonings and spills.
- Following label instructions helps you to minimize the risks and maximize the benefits.
Key Herbicide Safety Tips
- Read the entire label front to back.
- Follow the instructions.
- Review the instructions even for brands you know.
- Only apply the product where the label says it may be applied.
- Be precise in your application. More is not better.
The Label is the Law
ALWAYS read the label before using herbicide products. The label is a legal document that provides information on how to safely use the herbicide. This helps avoid harm to human health and the environment. Using an herbicide in off-label ways is illegal. It can result in legal enforcement actions.
READ THE LABEL & Follow Instructions
It has instructions to protect you and the environment.
- Labels are different for every product and they often change over time.
- Use a magnifying glass for small print.
- Pay attention to CAUTION, WARNING, and DANGER statements.
- Pay attention to the PRECAUTIONARY STATEMENTS.
- The law states you must read and follow herbicide instructions.
Protect Plants You Want to Keep
- Glyphosate and similar herbicide ingredients damage both grass and broadleaf plants.
- Minimize spraying of foliage, stems, exposed roots, or the trunks of desirable shrubs or trees to avoid harm.
- Follow the label to avoid damaging the roots of trees and shrubs.
Protect Yourself
Eye, skin & lung irritants
- Wear the right protective gear. This often includes chemical-resistant gloves, safety glasses, a long-sleeve shirt, pants, socks, and shoes.
- Mix outdoors or in a well-ventilated area.
- Wash hands after mixing or applying, and before eating or smoking.
- Take a shower immediately after handling herbicides.
- Wash clothes worn while mixing or applying separately from other laundry.
Avoid Wet, Windy, or Hot Weather
Use during favorable weather for best results.
- Don’t spray when it’s raining or when rain is expected in the next 24 hours.
- Wind causes spray to drift that can get on you and desired plants.
- Herbicides may be less effective in hot weather if the target plants are moisture-stressed.
- Some herbicides can turn into a vapor in hot weather and damage nearby plants.
Protect Children & Pets
Children and pets are at risk if they eat or touch the plants before it dries.
- Keep them away during and after applying herbicides (read label for how long).
- Remove toys and pet dishes from yard before applying.
- Don’t track herbicide products into your home on shoes or clothes.
Protect Pollinators
- Apply in the early morning or evening when bees are less active.
- Kill weeds before they flower. Avoid spraying flowering plants.
- Do not spray on bees or insects.
Storage & Disposal
- Store in a secure area away from children.
- Don’t put unused herbicide products in the trash.
- Never pour down any drain or waterway.
- Take unused herbicides to a hazardous waste facility.
Call 1-800-CLEANUP (1-800-253-2687) to find out where to dispose of herbicides.
For the Portland metro region in Oregon, contact Metro’s Recycling Information. Call 503-234-3000, email or visit Metro’s website
More about:
About Using Pesticides on School Grounds in Oregon
If using pesticides on school grounds, there are special rules in Oregon. See School Integrated Pest Management (Oregon Department of Agriculture).
NEED HELP?
The National Pesticide Information Center (NPIC) can answer questions about pest control chemicals.
1-800-858-7378 or npic@ace.orst.edu
Consider using a licensed pest or weed control company. Learn How to Hire a Pest Control Company.
Your local Extension Specialist in Oregon and other states can suggest other methods.
Content provided by Weston Miller and J. Jeremiah Mann. Pesticide safety information edited by Kaci Buhl.
Reviewed by OSU Department of Horticulture.
Grassy Weeds in Lawns References
Crabgrass
University of California IPM
Annual Bluegrass
University of California IPM
Quackgrass
Purdue University
Control of Annual Grassy Weeds in Lawns
Colorado State University Extension
Perennial Grassy Weeds in Lawns
University of Illinois Extension