Yellow nutsedge is a relatively common problem in lawns, especially in wet years or in lawns with irrigation. Although sedges look much like a grass, they are different.
Unlike grasses, sedges have triangular stems, and the leaves are three-ranked instead of two-ranked, which means the leaves come off the stems in three different directions. Yellow nutsedge is pale green to yellow and grows rapidly in the spring and early summer. Because of this rapid shoot growth, it sticks up above the rest of the lawn only a few days after mowing. This weed is a good indicator of poor drainage, but it can be introduced into well-drained sites through contaminated topsoil or nursery stock. As with many weeds, nutsedge is less competitive in a dense, healthy lawn than in an open, poor lawn.
Nutsedge is difficult to control culturally because it produces numerous tubers that give rise to new plants. Pulling nutsedge will increase the number of plants because dormant tubers are activated. However, it is possible to control nutsedge by pulling, but you must be persistent. If you are, eventually the nutsedge will die out though this will likely take more than one season.
If you were going to treat with an herbicide, it would be better to leave the nutsedge plants undisturbed so the herbicide can be maximally translocated to the roots, rhizomes, and tubers. Several herbicides are available for nutsedge control.
SedgeHammer and Hi-Yield Nutsedge & Horsetail Control contain halosulfuron and are effective and safe products. The SedgeHammer label says to apply after the nutsedge has reached the three- to eight-leaf stage. Waiting until this growth stage apparently results in improved translocation of the active ingredient to the underground tubers and rhizomes.
Products with sulfentrazone such as Bonide Sedge Ender, Ortho Nutsedge Killer and Spectracide Weed Stop for Lawns Plus Crabgrass Killer are also effective.
Research has shown that the first application should go down by June 21. If the initial spray is after June 21, mature daughter tubers may be stimulated to grow. (Ward Upham)
Field bindweed is difficult to control, especially for homeowners, but there are options.
Home Vegetable Gardens: Weed control requires taking the treated portion of the garden out of production for a time.
Glyphosate - Glyphosate is sold under a wide variety of names, the most common being Roundup. Take the garden out of production when treating.
1. Glyphosate is a non-selective herbicide that will kill whatever it hits but is inactivated when it contacts the soil.
2. Glyphosate is most effective when applied to bindweed that is at or beyond full bloom. You can treat earlier but don't skip the late summer to fall application.
3. Do not apply to bindweed that is under moisture stress or not growing well. The better the bindweed is growth, the more herbicide is taken up and the better the kill.
Turf: Selective herbicides are available. A herbicide with the active ingredient of quinclorac is now packaged in homeowner combination herbicides such as Fertilome Weed-Out with Q, Ortho Weed-B-Gon Max + Crabgrass Control, Monterey Crab-E-Rad Plus and Bayer All-in-One Lawn Weed and Crabgrass Killer.
Commercial applicator products include Drive, Eject, Facet and Paramount, all of which contain quinclorac. Combination products containing quinclorac include Q4, Quincept and Quinstar.
Products with quinclorac work better than glyphosate and are selective. Note that lawns treated with quinclorac should not use clippings in compost or as mulch as quinclorac is very stable on grass clippings.
We recommend clippings be returned to the lawn anyway but if they are bagged, they should be discarded. Do not apply products with quinclorac over exposed roots of trees and ornamentals. It would be best to avoid spraying beneath the canopy of any trees to avoid possible damage. If there are plans to convert a section of lawn to a vegetable garden, do not use quinclorac on that area. Eggplants can be damaged if planted within 12 months of areas treated with quinclorac, and tomatoes can be damaged if planted within 24 months.
Shrub Beds: Use a spray of glyphosate between plants. Use a shield if spraying near plants to keep spray from contacting green plant material. Remember, glyphosate will hurt your shrubs if it contacts green tissue.
It is possible to control field bindweed by pulling, but you must be extremely persistent. I remember reading a study from the 1940s that found that bindweed produces enough energy to start strengthening the roots when it reached the six-leaf stage. So, if pulling, never allow plants to produce more than six leaves. (Ward Upham)
Orchardgrass often infests tall fescue lawns. Unfortunately, orchardgrass is lighter green and faster growing than tall fescue, so it is very visible. Homeowners complain of the light green tufts of grass wherever this weed has become established. Even worse, there are no herbicides that will kill the orchard grass without also killing the turf. About the only good thing about orchardgrass is that it is a bunch grass and does not spread.
Orchardgrass often comes in as a contaminant in grass seed, especially K-31 tall fescue. Buying good grass seed is the first line of defense against this weed. Orchardgrass is a pasture grass and therefore is not found in the “weed seed” portion of the seed label. Rather, orchard- grass will be listed as “other crop seed.” Try to buy grass seed that has 0.0% “other crop seed.”
Control options are few and painful. Use glyphosate (Roundup, Killzall Weed and Grass Killer, Kleeraway Systemic Weed and Grass Killer and others) to spot spray orchardgrass clumps. Any lawn grasses you hit will be killed, so keep the spots sprayed as small as possible. Wait until the spots have turned brown and then cut out the clumps and replace with a small piece of sod. Large numbers of orchardgrass clumps may mean it is more practical to kill the entire lawn and start over. This should be done in the fall rather than now.
For information on identification of orchardgrass, including images, go to:
http://kswildflower.org/grass_details.php?grassID=15 (Ward Upham)
One of the most difficult weeds to control in lawns is the wild violet. Even combination products that contain 2,4-D, MCPP and Dicamba such as Trimec, Weed-Out and most formulations of Weed-B-Gon do not do a good job. Products with triclopyr give much better control though more than one treatment will likely be needed. A couple of products that contain triclopyr on the homeowner side are Turflon Ester and Weed-B-Gon Chickweed, Clover & Oxalis. (Note: There are several formulations of Weed-B-Gon but only Weed-B-Gon Chickweed, Clover & Oxalis contains triclopyr.)
Both products listed above are labeled for tall fescue and Kentucky bluegrass. Do not use products containing triclopyr on bermudagrass as severe injury will occur. Weed-B-Gon Chickweed Clover & Oxalis is labeled for buffalograss and zoysia (Turflon Ester is not) but lawns will likely show some temporary browning after application.
Spray only on calm days and when temperatures are below 90 degrees to avoid damage to nearby plants. (Ward Upham)
The other day after eating dinner I was watching TV trying to finally relax. A commercial came on about Roundup for Lawns…. I thought to myself, “Oh man! This is going to cause a lot of confusion!”
There is a huge difference in the active ingredients in Roundup compared to Roundup for Lawns. That is why it is so important to know what you are applying.
Dr. Kevin Frank at Michigan State University just posted a great article about the difference between Roundup and Roundup for Lawns. Check it out here.
Every homeowner needs to know the difference!
I will make a prediction. Due to the confusion with the names of these products, I will get at least one phone call this year where someone has killed their entire lawn with glyphosate because they thought they could use Roundup on their lawn and they put out the wrong product.
Always remember to READ THE LABEL for the correct rate, turfgrass tolerance, and specific instructions before application!!! (Jared Hoyle)
The plant with the little purple flowers that have been showing up in home lawns is called henbit. If you are not sure this is what you have, check the stems. If they are square rather than round, you have henbit. A plant that also is low growing but has round stems and tiny white flowers is chickweed.
Both these plants are winter annuals and start to grow in the fall. They spend the winter as small plants and so most people do not pay much attention to them until they start to flower in the spring. Trying to kill either one at this late stage with a herbicide usually is a waste of time and money. Though plants may be burned back, they will rarely be killed. So what should you do? Remember, these are winter annuals that will die as soon as the weather turns hot. Keep the lawn mowed until nature takes its course.
However, you can do something next fall that will help next spring. Henbit and chickweed usually germinate about mid-October. Spraying with 2,4-D, Weed-B-Gon, Weed Free Zone, Weed Out, or Trimec in late October to early November can go a long way toward eliminating these plants as they are small and relatively easy to control. Choose a day that is at least 50 degrees F so the young plants are actively growing and will take up the chemical.
Spot treating will probably be needed in the spring (March) to catch the few plants that germinate late. Use Weed Free Zone, Speed Zone, Weed Out, Weed-B-Gon, Trimec, or one of the special henbit herbicides early in the spring before they have put on much growth. (Ward Upham)
Crabgrass preventers are another name for preemergence herbicides that prevent crabgrass seeds from developing into mature plants. Many people have a somewhat foggy idea of how they work and assume they kill the weed seed. Such is not the case. They do not kill the seed or even keep the seed from germinating but rather kill the young plant after it germinates. Therefore, they do not prevent germination but prevent emergence.
Crabgrass preventers are just that – preventers. With few exceptions they have no effect on existing crabgrass plants, so they must be applied before germination. Additionally, preventers do not last forever once applied to the soil.
Microorganisms and natural processes begin to gradually break them down soon after they are applied. If some products are applied too early, they may have lost much of their strength by the time they are needed. Most crabgrass preventers are fairly ineffective after about 60 days, but there is considerable variation among products. (Dimension and Barricade last longer. See below.)
For most of Kansas, crabgrass typically begins to germinate around May 1 or a little later. April 15 is normally a good target date for applying preventer because it gives active ingredients time to evenly disperse in the soil before crabgrass germination starts. However, this year, we may want to go a week or two early. For southeast Kansas, this week would be appropriate, and for northwest Kansas, mid-April would be best.
Even better, base timing on the bloom of ornamental plants. The Eastern Redbud tree is a good choice for this purpose. When the trees in your area approach full bloom, apply crabgrass preventer. A follow-up application will be needed about 8 weeks later unless you are using Dimension or Barricade. Products that do require a follow-up application include pendimethalin (Scotts Halts) and Team (Hi-Yield Crabgrass Control).
Dimension and Barricade are the only two products that give season-long control of crabgrass from a single application. In fact, they can be applied much earlier than April 15 and still have sufficient residual strength to last the season. Barricade can even be applied in the fall for crabgrass control the next season.
Dimension can be applied as early as March 1. Because of the added flexibility in timing, these products are favorites of lawn care companies who have many customers to service in the spring. Though Dimension is usually not applied as early as Barricade, it is the herbicide of choice if it must be applied later than recommended. It is the exception to the rule that preemergence herbicides do not kill existing weeds. Dimension can kill crabgrass as long as it is young (two- to three-leaf stage). Dimension is also the best choice if treating a lawn that was planted late last fall. Normally a preemergence herbicide is not recommended unless the lawn has been mowed two to four times. But Dimension is kind to young tall fescue, perennial ryegrass, and Kentucky bluegrass seedlings and some formulations can be applied as early as two weeks after the first sign of germination. However, read the label of the specific product you wish to use to ensure that this use is allowed. Lawns established in the fall can be safely treated with Dimension the following spring even if they have not been mowed.
Note that products containing Dimension and Barricade may use the common name rather than the trade name. The common chemical name for Dimension is dithiopyr and for Barricade is prodiamine. Remember, when using any pesticide, read the label and follow instructions carefully.
We recommend crabgrass preventers be applied before fertilizer so that the grass isn’t encouraged to put on too much growth too early. However, it may be difficult to find products that contain preemergents without fertilizer. Those that don’t contain fertilizer are listed below. I didn’t find any products containing Barricade that did not also have a fertilizer. If anyone knows of other products that should be listed, let us know and we will publish them in a later newsletter.
- Scotts Halts
Team (Benefin + Trifluralin)
- Hi-Yield Crabgrass Control
- Hi-Yield Turf & Ornamental Weed and Grass Stopper
- Bonide Crabgrass & Weed Preventer
- Green Light Crabgrass Preventer
Video of the Week:
Ward Upham is the Kansas State Master Gardener Coordinator and runs the Horticulture Response Center. Other contributors include K-State Extension Specialists.