Grassy weeds are true grasses or monocots. A grass seed germinates and emerges as one single leaf. It develops hollow, rounded stems and nodes (joints)… Differentiating weeds from grass is important to treat the issue. How can you tell the difference? Annual grassy weeds are some of the more frustrating lawn weeds homeowners will encounter.
Grassy weeds are true grasses or monocots. A grass seed germinates and emerges as one single leaf. It develops hollow, rounded stems and nodes (joints) that are closed and hard. The leaf blades alternate on each side of the stem, are much longer than they are wide and have parallel veins.
A weed’s life cycle has great impact on the selection and success of a given control procedure, so it is important to learn the life cycle characteristics of a weed when you first learn its identity.
Annual weeds germinate from seeds, grow, flower, produce seeds and die in 12 months or less. Annual weeds are further categorized by the season in which they germinate and flourish. Winter annuals sprout in the fall, thrive during the winter and die in late spring or early summer. Summer or warm-season grasses such as crabgrass and goosegrass sprout in the spring and thrive in summer and early fall.
Perennial weeds are weeds that live more than two years. They reproduce from vegetative (non-seed) parts such as tubers, bulbs, rhizomes (underground stems) or stolons (above-ground stems), although some also produce seed. Perennial weeds are the most difficult to control because of their great reproductive potential and persistence.
Proper identification of weeds targeted for control is necessary in order to select effective control measures, whether cultural or chemical. Further assistance with weed identification is available from any Clemson Extension office.
Life Cycle & Description: Annual bluegrass (Poa annua) is a winter annual weed that emerges in early fall, persists through the winter, produces seed in early spring and then dies in late spring or early summer. Annual bluegrass reproduces by seed.
Annual bluegrass (Poa annua) is a cool weather annual grass weed that produces seed heads in the early spring.
Joey Williamson, ©2015 HGIC, Clemson Extension
Annual bluegrass prefers shady, moist sites and invades weak, thin lawn areas, especially low spots and flower beds where standing water occurs. It mainly germinates in late summer through early fall when nighttime air temperatures drop to the mid-70s. This usually occurs from September 15 to October 1 in the Coastal Plain and Sandhills areas, and September 1 to 15 in the Piedmont and Mountain areas. Further germination occurs in early winter with warm days and cold nights.
Annual bluegrass produces a white-colored, pyramid-shaped seedhead in the spring. It dies in the summer with the onset of high temperatures and/or dry conditions.
Annual bluegrass has smooth, apple-green leaves with two clear lines, one on each side of the midrib that run down the length of the leaf blade. The edges of the leaf tip curve inward like the front of a boat.
Control: Handpulling is a simple, practical approach for small areas. Improve the health and density of the lawn by fertilizing at the right time and with the correct amount; maintaining an appropriate soil pH; mowing at the recommended height; and watering properly. Apply a 2- to 3-inch layer of mulch to ornamental bed areas to suppress germinating weed seeds. Finally, improve surface drainage. Preemergence herbicides are available depending on the kind of turfgrass and ornamental plants grown. Apply preemergence herbicides to established lawns before the annual bluegrass seeds germinate. Once annual bluegrass emerges, preemergence herbicides are generally ineffective.
Selective postemergence herbicides are available for annual bluegrass control. These are best applied in November or early December when the weed is small, thus most susceptible to control. See Tables 1 & 2 for pre-emergence and post-emergence control. Apply all chemicals according to directions on the label.
Crabgrass & Goosegrass
Life Cycle & Description: Crabgrasses (Digitaria species) are summer annuals that germinate in the spring at about the time crabapple and forsythia bloom, when the air temperature is warm enough to promote crabgrass seed germination. They produce seed from midsummer to fall and are then killed by the first freeze in autumn. Crabgrass reproduces by seed.
Crabgrass can be identified by its tufted or prostrate growth habit, hairy stems, broad leaves and flower spikes with two to nine finger-like branches. This weed appears in disturbed areas, weak or thin turf areas and in edges of the lawn next to sidewalks and drives.
Goosegrass (Eleusine indica) is a tough, clump-forming summer annual with white to silver coloring near its base. Unlike crabgrass, goosegrass has flat stems and does not root at the lower nodes. It germinates a few weeks after crabgrass in late spring and produces seed from summer to early fall. The flowers and seeds are produced in two rows like a zipper on two to 13 finger-like branches at the top of the stem. Goosegrass is killed at the first freeze, and reproduces entirely from seed.
Goosegrass (Eleusine indica) can be identified by the white to silver color near the base of the grass clump.
Joey Williamson, ©2015 HGIC, Clemson Extension
Control: Handpulling is a simple, practical approach for small areas. Improve the health and density of the lawn by fertilizing at the right time and with the correct amount; reducing soil compaction; maintaining an appropriate soil pH; mowing at the recommended height; and watering properly. Apply a 2- to 3-inch layer of mulch to ornamental bed areas to suppress germinating weed seeds.
Preemergence and postemergence herbicides are available depending on the kind of turfgrass in your lawn. Preemergence herbicides provide about 2 to 2 1/4 months of control. Repeat applications would be required 60 days later for season-long control. Apply preemergence herbicides March 1 from the Coastal Plain to the Sandhills regions, and March 15 to 30 in the Piedmont and Mountain areas. Fall-seeded turfgrasses should not be treated with a preemergence herbicide until the following spring. See Tables 1 & 2 for pre-emergence and post-emergence control. Apply all chemicals according to directions on the label.
Life Cycle & Description: Southern sandbur, or sandspur (Cenchrus eschinatus), and field or coast sandspur (Cenchrus incertus) are summer annuals that germinate in the spring, grow during the summer and early fall and die with the first heavy frost. The name “sandspur” describes the sandpapery feel of their leaves and the spurs or burs that are produced from July until the first frost. Both reproduce by seeds. Sandspur tends to be more of a problem on sandy soils from the Coastal Plain westward to the Sandhills.
Control: Handpulling with gloved hands is a simple, practical approach to control sandspur in small areas. Improve the health and density of the lawn by fertilizing at the right time and with the correct amount; maintaining an appropriate soil pH; mowing at the recommended height; and watering properly. Apply a 2- to 3-inch layer of mulch to ornamental bed areas to suppress germinating weed seeds.
This annual weed can be controlled with a preemergence herbicide applied in early spring (March 1 in the Coastal areas to March 15 in Piedmont areas). Repeat in 60 days. Select an herbicide that can be safely used on your lawn.
See Tables 1 & 2 for pre-emergence and post-emergence control. Apply all chemicals according to directions on the label.
Table 1. Pre-emergence Herbicides to Prevent Grassy Weeds in Residential Lawns.
|Weeds Prevented||Active Ingredients||Examples of Brands & Products|
|Annual grass weeds including crabgrass & annual bluegrass||benefin||Pennington
|Same as for benefin, plus goosegrass||oryzalin||Southern Ag Surflan A.S. (40.4%)|
|Same as above||benefin + oryzalin||Helena XL2G (1% & 1%)
UPI Surflan [email protected] (1% & 1%)
Green Light Amaze Grass & Weed Preventer (1% & 1%)
|Summer annual grasses, annual bluegrass, some selected annual broadleaf weeds||benefin + trifluralin||Anderson Turf Products 2% Team Herbicide DG (1.33% &0.67%)
Hi-Yield Crabgrass Control
|Same as for benefin, plus oxalis & speedwell||pendimethalin||Anderson Turf Products 1.71% Pendimethal in DG
Scotts Halts Crabgrass & Grassy Weed
Harrell’s 0-0-10 with 0.86% Pendimethalin
|Same as for benefin, plus oxalis||dithiopyr||Anderson Turf Products 0.25% Pendimethal in DG
Bonide Crabgrass & Weed Preventer for Lawns & Ornamental Beds (0.27%)
Hi Yield Turf & Ornamental Weed & Grass Stopper Containing Dimension (0.125%)
StaGreen CrabEx Crabgrass & Weed Preventer (0.25%)
|summer annual grasses, annual bluegrass, some selected weeds such as chickweed, spurge, goosegrass||prodiamine||Helena Pro-Mate Barricade & Fertilizer 0-0-7 (available with 0.22, 0.375, or 0.435%)
Howard Johnson Crabgrass Control with Prodiamine & 0-0-7 (0.86%)
Lebanon Pro Fertilizer (0-0-7) with Prodiamine (0.38% or 0.43%)
Lesco Stonewall Plus Fertilizer (0-0-7) (available with 0.20, 0.29, 0.37, or 0.43%)
Lesco Barricade Plus Fertilizer 0-0-7 (0.43%)
Scotts Halts Pro 0-0-7 & Halts Pro (0.28%)
Harrell’s 0-0-7 with 0.21% Barricade
Harrell’s 0-0-7 with 0.30% Barricade
Harrell’s 0-0-7 with 0.45% Barricade
Southern States Pro Turf 0-0-7 with 0.38% Barricade
Table 2. Post-emergence Herbicides to Control Existing Grassy Weeds in Residential Lawns.
|Weeds Controlled||Active Ingredients||Examples of Brands & Products|
|annual & perennial grasses, such as crabgrass, foxtails, goosegrass, sandbur; bermudagrass suppression||fenoxaprop
(for fescue lawns only)
|Aventis Acclaim Extra
Bayer Advanced Crabgrass Concentrate (6.59%) Killer for Lawns RTS (0.41%)
|annual & perennial grasses control. Excellent control of crabgrass; good control of bermudagrass, sandspur, bahiagrass & goosegrass||sethoxydim
(for centipedegrass lawns only)
|Arrest (by Whitehall Institute) (13%)
Segment (by BASF) (13%)
|Excellent control of crabgrass; fair control of dallisgrass, foxtails, & signalgrass. Also, most broadleaf weeds, such as dollarweed, black medic, wild onion & garlic, speedwells, plantains, dandelion, white clover, violets, henbit, chickweed, star of Bethlehem||quinclorac + 2,4-D + dicamba (for fescue, zoysiagrass, & bermudagrass 1 )||Bayer Advanced All-in-One Lawn Weed & Crabgrass Killer Concentrate
Bonide Weed Beater Plus Crabgrass & Broadleaf Weed Killer RTS
Ferti-lome Weed Out with Crabgrass Control RTS
Monterey Crab-E-Rad Plus RTS
Ortho Weed B Gon Max Plus Crabgrass
|Excellent control of crabgrass; fair control of dallisgrass, foxtails, & signalgrass. Also most broadleaf weeds, such as dollarweed, black medic, speedwells, plantains, dandelion, white clover, violets, henbit, chickweed, star of Bethlehem, & nutsedges.||quinclorac + 2,4-D +
dicamba + sulfentrazone
(for fescue, zoysiagrass & bermudagrass 1 )
|Spectracide Weed Stop for Lawns Plus
Crabgrass Killer RTS
|Excellent control of crabgrass; fair control of dallisgrass, foxtails, & signalgrass; Also, some broadleaf weeds, such as dollarweed, black medic, violets, speedwells, dandelion, white clover, nutsedges, chickweed, star of Bethlehem, & henbit.||quinclorac + sulfentrazone
(for fescue, zoysiagrass & bermudagrass 1 )
|Image Kills Crabgrass – Water Dissolving Granules|
|Very good control of annual bluegrass; fair control of crabgrass, sandspur, bahiagrass, fescue, & bermudagrass; poor control of goosegrass, & dallisgrass. Also many broadleaf weeds.||atrazine (for St. Augustinegrass & centipedegrass)||Hi-Yield Atrazine Weed Killer (4.0%) Concentrate
Southern Ag Atrazine St. Augustine Weed Killer (4.0%) Concentrate
Image Herbicide for St. Augustine &
Centipede with Atrazine RTS (4.0%)
|Annual & perennial grass control, including bermudagrass, crabgrass, foxtail, goosegrass, torpedograss, johnsongrass||fluazifop-
P-butyl (for Tall Fescue & Zoysiagrass
|Gordon’s Ornamec 170 Grass Herbicide (1.7%)|
|1 Products containing quinclorac may cause temporary yellowing or discoloration of bermudagrass.|
Pesticides are updated annually. Last updates were done on 7/22 by Barbara Smith.
Originally published 09/99
If this document didn’t answer your questions, please contact HGIC at [email protected] or 1-888-656-9988.
Robert F. Polomski, PhD, Associate Extension Specialist, Clemson University
Bert McCarty, PhD, Turf Specialist, Clemson University
This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.
10 Weeds That Look Like Grass
Mother Nature can be a clever mistress, indeed. She can be so clever that she can disguise a variety of different common weeds that look like desirable grasses.
An invasion of such a grassy weed is insidious. It doesn’t appear to be a serious problem for your lawn until it’s already become a serious problem.
These weeds hide in plain sight and can be easily overlooked if you don’t know what you’re looking for.
That’s what this article is all about. We are going to provide you with a list of weeds that look like grass. You’ll discover how to identify each grassy weed and learn some different control methods for each one.
So, before these common weeds that look like common lawn grasses become an issue, let’s dive in and take a look.
1. Annual Bluegrass (Poa annua)
What it Looks Like
Annual bluegrass (Poa annua) is one of the most commonly misidentified weed grasses. It is a close relative of the desirable cold-season Kentucky bluegrass.
As with all members of the Poa genus, annual bluegrass has canoe-shaped tips on its grass blades. Because they mimic the shape of other Poa species, the best way to identify these grassy weeds is to look for their brighter and lighter green color.
Annual bluegrass also has a long ligule, or membrane, that connects that leaf blade to the base of the stem.
Annual bluegrass is also a cold-season weed grass. They tend to congregate in shady areas with excess moisture. The heat and light from the sun will dry these grassy weeds out and leave bare patches in your yard.
Annual bluegrass can be treated with both pre-emergent and post-emergent herbicides. However, the best way to ensure that you don’t have it hiding on your lawn is to create a habitat not suitable for its growth.
If you have areas of your yard that are shaded, open them up by trimming back the trees or shrubs that provide the shade. For moist areas, ensure that the soil isn’t compacted and is properly draining. These two prevention methods should do your grass justice and keep annual bluegrass at bay.
2. Crabgrass (Digitaria sanguinalis and Digitaria ischaemum)
What it Looks Like
If you’ve not heard of crabgrass, then you’re not spending enough time outside. Because these grassy weeds are everywhere. Digitaria sanguinalis (also called large crabgrass) is predominantly found in the northern part of the country, and Digitaria ischaemum (also called smooth crabgrass) is the crabgrass species that dominates the southern part.
But crabgrass is crabgrass. And none of it’s good. This grassy weed makes its home on unhealthy yards. So if your lawn is under-watered, under-fed, and poorly drained, then you’re probably going to have a problem with crabgrass.
Crabgrass plants are annual weeds that will die off each year. That may sound like good news until you hear that each crabgrass plant is capable of producing more than 150,000 seeds that can germinate every spring.
Crabgrass grows in clumps on your lawn. While it does look similar to normal grasses, it has a much thicker growth habit and is altogether an unattractive eyesore on your lawn. If the seeds do germinate and grow unchecked, the blades can grow as long as 2 feet. Crabgrass is generally a lighter green than most desirable lawn grasses. Once its root system is established, it spreads quickly and aggressively across your lawn.
Just like annual bluegrass, you can get rid of crabgrass with one of many selective pre-emergent herbicides to prevent the seemingly countless seeds from germinating. If you’re too late for that, a selective post-emergent herbicide will also clear up the problem. However, your best bet if the seeds have already germinated is to recognize and pull the crabgrass plants before they’re old enough to go to seed.
The best defense, however, is a good offense. And a good offense, in this case, is ensuring that your lawn is healthy and thick. Take care to ensure proper fertlization, watering, and drainage on your property. This will keep your desirable grass too thick and healthy for crabgrass to invade.
3. Yellow Nutsedge (Cyperus esculentus)
What it Looks Like
Yellow nutsedge is a perennial weed that can attack your lawn from above the soil and below. Seeds can be spread through the air from above the soil level and through its rhizomes, or tubers, below the soil’s surface.
The fact that it’s a perennial weed that will reappear each growing season only complicates matters further.
When yellow nutsedge is young, it will have light green colored grass blades. As it ages, the grass blades will become a deeper green. This change in color can make it hard to identify amongst your desirable lawn grass.
Yellow nutsedge is best identified by looking at its root system. On its roots, there will be nut-like tubers growing from them. These tubers give the grassy weed its name.
The best plan of action for controlling yellow nutsedge is to keep your lawn lush and healthy. A healthy lawn will do its own work and prevent nutsedge from having a place to invade. So be sure to do the upkeep using proper maintenance practices, and you should be fine.
Since yellow nutsedge is a perennial grassy weed, once it shows up on your lawn, the best way of getting rid of it is a heavy dose of post-emergent herbicide.
Pulling the weeds may cause you more problems because leaving the smallest piece of these plants in the soil guarantees that they will regenerate and make a repeat appearance on your lawn. If you decide to go this route, ensure that you remove every single fiber of the yellow nutsedge from the ground.
4. Green Foxtail (Setaria viridis)
What it Looks Like
Green foxtail earns its name because, once it is fully grown, a piece of the plant resembles the tail of a fox. This piece that resembles a fox tail is a seedhead that can produce hundreds of problematic seeds that can spread through your lawn and garden.
Green foxtail is an annual grassy weed that will require the germination and growth of brand new plants every year.
Identification can be tough before the plant grows its seedhead. Its blades are a normal green color and don’t have a remarkably different shape than most desirable lawn grasses. Its growth habit is normal as well. So this one can be tough to spot.
Since it’s an annual weed, you can control green foxtail by pulling it out. Preferably, you’ll have it removed before it goes to seed. But, as you already know, this can be a difficult task because it looks so similar to your grass before that point.
If you find that green foxtail has already gone to seed, you can pull the plant from the soil and use a pre-emergent herbicide to keep the green foxtail’s seeds from germinating in the spring.
If the invasion is too great to pull all of the grassy weed out, you can use a selective post-emergent herbicide to kill it off. You’ll still need to treat the ground with a pre-emergent herbicide at some point before the seeds begin to germinate when the weather warms up.
5. Creeping Bentgrass (Agrostis stolonifera)
What it Looks Like
Creeping bentgrass is often planted intentionally. But this intentional planting is usually relegated to the fairways and putting greens on manicured golf courses and not on your yard.
Creeping bentgrass can spread aggressively in your grass and garden through its stolons.
Creeping bentgrass will appear in light green patches in your grass. Its blades are generally finer and thinner than most desirable grasses. If you allow creeping bentgrass to grow taller than 1 inch, it will take on a puffed-up or swollen appearance.
Cool-season creeping bentgrass is averse to excessive heat and will turn brown quickly at even slight elevations in temperature.
Because creeping bentgrass propagates and spreads through its stolons beneath the soil’s surface, one plan of attack is to use selective herbicides on this hardy perennial plant. An herbicide containing glyphosate is your best bet. However, this may only work if you catch these lawn weeds very early in their life cycle.
Creeping bentgrass is often more widespread than it may seem. This is due to it spreading underground through its stolons. On average, if you have a patch of creeping bentgrass with a diameter of 1 foot, you actually have a mix of the grassy weed and your desirable grass that extends three times that diameter. This makes spot-treating creeping bentgrass very difficult.
Unfortunately, the nature of these weeds makes them very difficult to completely eradicate once they are established. So, you’re either going to have to start over by removing all the grass entirely and reseeding or start promoting the growth of creeping bentgrass on your property.
To promote creeping bentgrass, you’ll need to shift your focus from soil fertility and nutrition to pest control. Because pests are one of this weed’s primary afflictions.
6. Common Couch (Elymus repens)
What it Looks Like
Common couch is a hardy perennial grassy weed that also goes by couchgrass and quackgrass. These weeds are equally at home in shade and sun.
Common couch spreads through both its underground rhizomes and its airborne seeds. Once it is established, its root system becomes exceedingly difficult to remove completely. So, it’s best if you can catch it early.
Common couch has a coarse texture and will appear on your lawn in patches. It’s blue-green color can be hard to distinguish amongst some desirable grasses.
The blades of these grassy weeds look similar to fingers. Their growth habit wraps these finger-like blades around the stem at the base of the plant.
If it is allowed to grow unchecked, common couch will take over your lawn in no time. It makes its home on areas that are thinned or bare. So, an unhealthy lawn makes the perfect victim for these weeds.
Whenever you come across common couch in your lawn or garden, you can pull it up by hand. But, if you do, you need to ensure that every piece of the plant is removed from the soil. Otherwise, you’re destined for another visit as soon as it can regenerate.
Chemical control will require both pre-emergent and post-emergent herbicides because it spreads underground through its rhizomes. So you have to ensure that the hardy root system is dead to prevent its propagation.
The best defense against common couch (and this feels like it’s becoming a theme) is a healthy, vibrant, and thick lawn. It will outgrow the weeds, and they won’t have any space to invade.
7. Smooth Bromegrass (Bromus inermis)
What it Looks Like
Just like couchgrass, smooth bromegrass is a perennial weed that can spread through either rhizomes or seeds. It also has a robust root system that will be difficult to get rid of once it becomes established in your lawn.
Smooth bromegrass can grow to heights of over 7 feet. Its blades, or leaves, grow to between 8 inches and 2 feet long. The blades hang down in a drooping manner. The blades are covered on both the upper and lower surfaces by fine hairs.
This weed’s color ranges from a light to a normal shade of green. The upper portions of the blades can be lighter in color because of their length if growing conditions are poor.
Fortunately, you can control smooth bromegrass by keeping it cut short with your mower or weedeater. Keeping it short will allow your desirable grass to crowd it out eventually, and you won’t have to resort to any chemical herbicides.
However, if the weeds have spread out and established themselves, you’ll need to use some strong pre-emergent and post-emergent herbicides to quell the invasion. Use an herbicide with glyphosate for the best results.
8. Carpetgrass (Axonopus compresus and Axonopus affinis)
What it Looks Like
These weeds share the same genus and have similar physical traits, so they’re lumped together under one name. Carpetgrass is a perennial weed that can grow to heights of a foot or more. It will appear on your lawn in very thick mats that are shaded a normal green color.
In the summer, they will produce seed heads that look very similar to those of crabgrass. The seed heads will be taller than the rest of the plant.
Carpetgrass prefers acidic soil with high moisture content. You will probably find them congregating and growing in shady areas that do not receive adequate sunlight. This allows the moisture levels to build up in the soil.
One good thing about carpetgrass is that you can control it through natural methods. All you have to do is raise the pH level of the soil. You can do this by adding lime or salt mixed with a gallon of water. One of these two should do the trick.
Of course, if you catch it early enough, you can pull it from the earth. However, since it is a perennial weed, you’ll need to ensure that you remove every last piece of it from the ground.
9. Tall Fescue (Festuca arundinacea)
What it Looks Like
This may be confusing because tall fescue is used as a desirable grass on some lawns. However, much like creeping bentgrass, it can show up without an invitation and take over your lawn. Ironically, the very things that make this such a desirable grass are also the things that make it a worthy opponent in your yard.
Tall fescue has distinct blades or leaves. The leaves of tall fescue are thick and broad. They have pronounced veins running the length of the blades, and this gives them a coarse texture. The blades are colored bright green, and the lower surface is a lighter green than the upper surface.
When it comes to tall fescue, I have some good news and some bad news. The bad news is that it is an extremely hardy plant that is very drought resistant. Once it shows up in your grass, it can be challenging to remove it completely.
It spreads through underground rhizomes, so its initial damage assessment may be underestimated. It can be spread further than it appears at first.
The good news is that you can beat tall fescue with natural means. Solarization is the best technique to use. Cover the weeds up with black plastic, newspaper, a tarp, or cardboard and let the heat, combined with a lack of sunlight and oxygen, suffocate the invasion out of your yard.
10. Johnsongrass (Sorghum halepense)
What it Looks Like
Johnsongrass is a perennial weed that is relatively easy to identify and control, which is a different story than the rest of the perennial weeds in this article.
When johnsongrass is in its early stages of life, it resembles the seedlings of the corn plant we all know and love. Left to grow unchecked, it can reach heights of over 7 feet.
Its seed head will start out green and then transition to a purplish maroon color.
As johnsongrass matures on your lawn, you’ll be able to pick it out because its leaves will become up to an inch thick and have a distinct white vein running down the middle of each blade.
There’s an easy way to control it and a hard, labor-intensive way to control it. The easy way is to cover the entire plant with highly concentrated vinegar. Be careful not to spray anything you don’t want to kill because vinegar is non-selective.
The hard, labor-intensive control method is used for larger johnsongrass invasions. It spreads through its rhizomes under the soil along with its seeds. So, to kill the johnsongrass, you’ll need to expose those rhizomes to the elements by using a tiller to cultivate the earth containing them. Do this later in the fall and expose the rhizomes to the cold winter temperatures, and they won’t be making a second appearance in the spring.
Jeffrey Douglas own a landscaping company and has been in the business for over 20 years. He loves all things related to lawns or gardens and believes that proper maintenance is the key to preventing problems in the first place.
Annual Grassy Weeds
Identification and Control
– Crabgrass and Foxtail Weeds –
Let’s look first at crabgrass. Most grassy weeds are undesirable weedy grasses that germinate and grow in lawns, but can lower turf quality and appearance. These weeds do not have the characteristics or growth habits that produce a quality lawn.
Annual grass-type weeds are those that germinate from seed each year and die at the end of the growing season. Annual weeds are prolific seed producers since seed germination is the method of producing the next year’s generation of plants.
Crabgrass (Late Spring Annual Weed)
- One of the most common and troubling grassy weeds.
- Yellow-green to a darker blue-green in color.
- Can be prostrate or upright growing.
- Multi-branched stems. Large crabgrass roots at the nodes.
- One plant can produce over 150,000 seeds.
- It doesn’t make a good lawn because it doesn’t take off until late spring or early summer and dies with the first heavy frost.
- Plants start off sparse but increase in number and size by end of the year.
- Can be difficult to stop once they start growing.
The U.S. and Canada have many grassy weeds with crabgrass being one the most problematic. There are two major species of crabgrass: smooth crabgrass (also called small crabgrass) and large crabgrass (also called hairy or common crabgrass). Smooth crabgrass is found mostly in the northern half of the U.S. and large crabgrass is found throughout the U.S. and southern Canada.
All crabgrass varieties are summer annuals that must come back each year by seed. It is a full sun grassy weed and will only tolerate very light, partial shade. It will not grow in shaded areas.
Crabgrass was originally introduced into this country as a possible forage crop. However, it easily escaped cultivation and is now widespread throughout the country. It is one of the most common and problematic weedy grasses in home lawns. It is also found on golf courses, parks, flower and vegetable gardens, athletic fields and any other place that seeds are able to germinate.
Crabgrass is most at home in areas of thin or poor quality turf. The plants grow quickly and can cover an entire yard by the end of summer.
Crabgrass is yellow-green in color with short, wide leaves. While the seedling look similar to other plants, they soon begin to distinguish themselves. In young plants, like the one in the photo to the left, the leaves are twice as long as they are wide. These young plants begin by growing prostrate with three or four stems branching out in a starfish pattern. As the plant matures the stems will curve in an upward direction. Each plant can produce as many as 700 new tillers (new leaf blades). At full maturity, each leaf will grow to be a few inches long. Crabgrass leaves have tiny hairs on both sides of the leaves.
The roots are shallow and fibrous and do not reach the depth of many other grasses. Large (hairy) crabgrass will root at the nodes and can produce long stolons. Smooth crabgrass does not root at the nodes.
The shallow root system works in their favor by absorbing as much water as possible before it reaches the deeper rooted plants. Frequent, shallow watering will cause crabgrass to flourish at the expense of other grasses. Less frequent, deep watering is better for your turfgrass, but will not neccessarily hinder crabgrass growth.
The photo above is of a mature crabgrass plant, while the photo below is of common bermudagrass.
The leaves of bermudagrass are much finer and are darker in color. Crabgrass seed heads are finger-like spikes that resemble common bermudagrass seed heads. However, crabgrass seed heads are somewhat thicker.
There are usually three to seven spikes that can either be folded up like a funnel or spread out in a whorl pattern. Each plant can produce as much as 150,000 seeds a year. Crabgrass germinates from seed each year when soil temperatures reach 55 degrees for five consecutive days. The blooming of forsythia in your area closely coincides with the germination of crabgrass seeds.
Once the seed has germinated, crabgrass becomes difficult to control. Because of the prostrate growth habit, crabgrass can produce seed heads at mowing heights as low as ½ inch. Mowing your lawn at a height lower than is healthy for your particular grass will only benefit and encourage crabgrass growth.
Cultural Practices that Help Prevent Grassy Weeds
Crabgrass, like many there grassy weeds, do not like competition from turfgrass. Crabgrass grows best in poor quality lawns, lawns cut and maintained too short, lawns with disease or insects damage, and in high traffic areas. Lawns with thin or deteriorating grass will give the seed plenty of sun, heat and space for seed germination. A poorly maintained lawn will guarantee that you will have increasing problems with broadleaf and grassy weeds.
If crabgrass is a problem, avoid fertilizing in late spring and summer. Especially avoid applications of high Phosphorus fertilizers. Phosphorus is essential for seedling growth and will only promote crabgrass establishment.
The best method of keeping crabgrass and other grassy weeds out of your lawn is to build a thick, healthy, vigorously growing turf. The first step is to ensure you have the right grass type for your area. Increasing the grass thickness can be accomplished by overseeding, plugging or laying sod, proper fertilization and irrigation. Until the lawn thickens, grassy weeds will continue to be a problem.
It is also important to mow your lawn at the highest recommend level for your specific grass type. This will shade the soil and make germination more difficult. Many cool season turf grasses can be mowed at a height of 3 to 4 inches. Depending on your grass type, see the Cool Season Grasses or the Warm Season Grasses Warm Season Grasses sections of this site for helpful mowing and planting information.
You may find it necessary to use a preemergent herbicide to prevent the seeds grassy weeds and other weeds from germinating.
The most effective and proven method of preventing crabgrass from starting is to use a preemergent herbicide. I can’t stress this enough. If you want to prevent crabgrass from ever starting, you have to use a preemergent.
Preemergents are an added ingredient in many spring fertilizer. The bags will be labeled “with Crabgrass Control” or “Crabgrass Preventer”, etc. Make sure you spread the fertilizer at the correct nitrogen (N) level for your grass type. For help developing a sound fertilizer program, read the page on Developing a Fertilizer Program.
A preemergent must be applied before the crabgrass seeds germinate in spring. Again, it MUST be applied before they germinate with only one exception, the use of Dimension preemergent will kill the crabgrass at very early seedling stages. I will describe this in better detail below.
A preemergent (also spelled pre-emergent or pre-emergence) herbicide works by preventing cell division on young plants. A preemergent doesn’t actually prevent the seeds from germinating, as commonly believed. However, once the seeds do germinate, the chemical prevents the cells from dividing and the seed dies. In this way, the seeds are destroyed. An important note: Preemergents will have the same effect on most lawn grass seeds as well. Do not overseed directly before or within a few months after herbicide application or your seed may be ruined.
If you have waited too long and the crabgrass begins growing, preemergents usually have no effect. However, there is one product with the trade name “Dimension” (Chemical name: dithiopyr) that will give some control of seedling plants for a few weeks after emerging from the soil.
The effectiveness of some homeowner type preemergent herbicides is questionable. Some brands don’t perform as well as others. The effectiveness is also related to how it was applied, the amount and frequency of irrigation, amount of rain received, etc.
Keep in mind, if applied too early, the chemical can breakdown too soon allowing mid to late season seeds to germinate. Other chemicals have a short life span and it must be reapplied in mid-summer. Therefore, timing of the application is very important. Outside temperature and soil temperature are important. Remember, crabgrass germinates when soil temperatures reach 55 degrees for five days in the top inch of soil. It is okay to water after the preemergent has been put down, but don’t over water or water too frequently. Frequent, heavy irrigation or heavy rain places maximum stress on these herbicides.
For Established Weeds
Once the weeds are established, they are very difficult to control. Post-emergent herbicides labeled for grassy weeds will need to be used. Most products will require several applications for complete control. Products with MSMA or DSMA will control crabgrass as well as other weedy grasses. The Ortho company makes a product with these active ingredients. Add the correct amount of a “sticker/spreader” to the herbicide mixture for better adherence and absorption into the plant.
There is also the herbicide quinclorac under the trade name “Drive”. This is now available to homeowners and sold by Ortho under the name “Weed-B-Gon MAX Plus Crabgrass Control Ready To Use”. It contains other ingredients to help control broadleaf weeds as well.
The most popular preemergent for crabgrass and other grassy weeds is Corn Gluten Meal. Nick Christians, a turf specialist and university professor in Iowa, holds the patent.
Corn Gluten Meal is sometimes marketed as an organic weed killer for broadleaf and grassy weeds. Although it actually holds little or no weed killing properties it is, however, an effective preemergent. It works by robbing the moisture from developing germinated seeds and seedlings.
One main difference between chemical preemergents and corn gluten meal is the amount applied. Corn gluten meal must be applied between 10 to 30 lbs 1000/sq.ft. Generally, 20 lbs/1000 sq. ft. is the average for most lawns. Use more for severe weed problems. It does not require a license to use.
Timing is important and it must go down near the time that seeds will germinate. After application, irrigate the corn gluten and allow a drying period. This is critical for effectiveness because it must absorb the surface moisture. In wet climates, such as the north western U.S., corn gluten meal may not be as effective. A second application can be made in the fall.
Keep in mind, with corn being used as fuel for vehicles, corn gluten meal is rising in cost. Shop for the best price.
Learn From the Mistakes of Others: Spraying your lawn with a a non-selective herbicide such as Round-up, etc is not an effective crabgrass control. It doesn’t harm the seeds in the soil. Although it will kill all the grass and weeds it touches, the following year you will still have the problem with crabgrass and other broadleaf and grassy weeds that start from seed.
For lawns containing 50% or more weeds with thin or very little grass, a non-selective herbicide can be used if you plan on seeding or sodding soon after. Don’t wait too long to renovate or the weeds will become established and you will have to do it again. Each grass type has a preferred time of year when it should be planted.
Read labels carefully and follow all label instructions. Note that MSMA and DSMA are not recommended for St. Augustinegrass, centipedegrass or carpetgrass.
Yellow and Green Foxtails (Summer Annual Weed)
Foxtails are a summer annual grassy weed. They get their name from the seedhead that resembles a fox’s tail. They can spread quickly in sunny areas but less so in shade. The same preemergents that control crabgrass will also control foxtails.
- Grassy weeds with characteristic cylindrical seed heads.
- Yellowish-green to blue-green leaves.
- Seed heads are 2-3 inch.
- Reproduces from seed only.
- Difficult to control once seeds have germinated.
- You will start to see foxtails as soon as the crabgrass weeds are well-established.
- The same preemergent that stops crabgrass also stops foxtails.
Foxtails are a species of warm season, annual grassy weeds that starts from seed. It grows in full sun, but can tolerate very light, partial shade. It will not grow in shaded areas.
It develops from a fibrous root system and has a prostrate to upright growth habit. With mature plants, it is common to see the stems branching out at the base, remain prostrate for an inch or two and then curve upward at a 30 to 70 degree angle. Each plant can produce multiple stems that can easily grow twice the height of the leaves.
The coarse leaves are a yellowish-green to a darker blue-green color. They can grow to 12 inches long and up to ½ inch wide. The leaves are flat and smooth. The widest part of the blade is at the base. The leaves have small silky hairs on the upper surface near the base.
Foxtails are known for their characteristic seed head that has a foxtail-like appearance. The seed head is at the end of the stalk and usually extends several inches above the leaves. Mature plant can have a dozen or more seed heads and can produce thousands of seeds each year. Seeds germinate when temperatures reach 68 degrees and will continue germinating through most of the summer. Foxtails will die at the first killing frost.
Giant foxtail is another foxtail species that grows 2-5 ft tall, but it cannot take repeated mowing. For this reason, giant foxtail is rarely found in mowed turf. Notice that the seed head of giant foxtail droops, while yellow and green foxtail seed heads do not.
The primary way of preventing the establishment and spread of foxtail is to maintain a thick, healthy lawn. Maintaining your lawn at the tallest mowing height recommended for your grass type will help slow seed germination.
Consistent, weekly mowing to remove the seed heads before they mature will also go a long way to deter spread. If you have only a few plants growing in your lawn, try removing them by pulling them up. The plant has a fibrous root system, however, some plants will root at the nodes near the base of the plant.
If you have had problems before with foxtails, the best way to stop their development is with a preemergent herbicide. These preemergents are added to spring fertilzers.
The same herbicides labeled for crabgrass will work on many other grassy weeds, including foxtails. Preemergents are added to spring fertilizer and will be labeled “with Crabgrass Control” or “Crabgrass Preventer”, etc. Always check the label before using, however. Once the preemergent had been applied, moisture in the soil will activate it. Fertilizers need to be applied correctly in the amounts needed for your grass type and time of year. Scotts fertilizer brand as well as a few others are good homeowner fertilizers. Bargain brands may not give you the control over grassy weeds that you would like. Since fertilizer applicatons are based on the Nitrogen (N) needs of the grass you will need to know how much to apply. Click on the link for helpful information on Developing a Fertilizer Program.
Most preemergents are designed to last a few months before they begin to lose effectiveness. Not all active ingredients work equally well or have the same duration and homeowner varieties tend to last the least amount of time. This means that your timing will be very important. Important Note: Foxtails will germinate a few weeks to a month later than crabgrass. Something to remember when applying a preemgerent.
Once the seed germinates, the herbicide chemical stops cell division within the seed, so the plant never develops. As a result, the seed dies.
The preemergent herbicide label may list other broadleaf and grassy weeds that it controls. However, most are not very effective with broadleaf weed seeds.
For Established Weeds
Post-emergence herbicides will be needed once the foxtails have become established. The herbicides containing the active ingredients MSMA or MSDA are labeled for many grassy weeds, including foxtails. Read the label carefully and follow all label instructions. MSMA and DSMA are not recommended for use on St. Augustinegrass, centipedegrass or carpetgrass.
There is also the herbicide quinclorac under the trade name “Drive”. This is now available to homeowners and sold by Ortho under the name “Weed-B-Gon MAX Plus Crabgrass/Grassy Weeds Control. It is a “Ready To Use” formulation, meaning it comes already pre-mixed. It contains other ingredients including 2,4-D and Dicamba to help control broadleaf weeds as well.
Nimblewill Grassy Weed
Nimblewill is a grassy weed that resembles bermudagrass. It is most prominent when growing in cool season grasses. Find information on identification, growth habits, and control methods.
Winter Annual Broadleaf Weeds
With each spring comes a surge of winter annual broadleaf weeds. Here you will find valuable information about these difficult weeds including growth habits, photos, and measures that can be taken to control them.
Summer Annual Broadleaf Weeds
Many of the most problematic broadleaf weeds are annuals. Here you will find specific summer annual weed information, with weed names, photos and control methods.
Perennial Broadleaf Weed Identification Page 1
Click here for weed identification and control of common broadleaf perennial lawn weeds. This page has detailed information on Canada Thistle, Mouseear Chickweed, White clover, Dandelion, Field Bindweed, Ground Ivy, and Common Mallow.
Perennial Broadleaf Weed Identification Page 2
This page contains more perennial broadleaf weed identification and control methods. You can find detailed information on Buckhorn Plantain, Broadleaf Plantain, Red Sorrel, Wild Violets, and Common Yarrow.
Yellow and Purple Nutsedge
Nutsedge is a summer perennial grass-like weed. They can be particular problematic since they cannot be controlled by broadleaf weed herbicides. Click here for weed identification, growth habits and control methods.