Questions on: Quackgrass & Crabgrass
Ron Smith, Horticulturist, NDSU Extension Service
Q: We have a sloped area in our yard. Weíre looking for a flowering, low-growing ground cover. Itís in a sunny area and has good soil. What do you recommend? Also, we have a lot of crabgrass and quackgrass. What would you recommend to control it and when to apply it in the spring? We enjoy reading Hortiscope. (Browns Valley, Minn.)
A: Thank you, Iím glad you enjoy the column! Quackgrass is going to be difficult to control, but give it a try. Next spring before you plant, spray the quackgrass with Roundup when it is 3 to 4 inches tall. That will at least slow it down. Chokeberry, bird's foot trefoil, moneywort and lily of the valley are some plants you may want to consider. Thank you for your interest!
Q: We have a massive infestation of crab grass in our lawn. We had someone come to look at it and were advised to treat it with a pre-emergence in the spring. However, we are wondering if there is something we could do now to prevent it from spreading further or to at least prevent it from transferring nutrients to the roots. Thanks for any help you can give us. (Jamestown, N.D.)
A: Don't waste your money doing it now because the frost will kill it. A pre-emergent is the best treatment for control. If you are planning to reseed at the same time, by sure to use Siduron (Tupersan) as the material so the desirable grass seed will not be inhibited from germinating.
Q: I bought a new house in West Fargo three years ago. The first year, I sprayed the yard twice with Roundup to kill the weeds. The next spring, I had problems with the sprinkler system that I had installed, so the weeds grew again. I resprayed with Roundup. In late July, I leveled the yard, planted a quality grass seed and started growing a lawn. I have been spraying the quack grass for two years, but this year is the worst. I have more of the weed than I had the last two years. I water the lawn four times per week and fertilize. Last spring, I applied Scottís Turf Builder with "halt," but I am still losing the battle. Do you have any suggestions short of killing the entire lawn and starting over? (e-mail reference)
A: I'm sorry to tell you that it is a losing battle. I know from experience. I have killed my lawn three times in the past 21 years. Each time I thought the quack grass was eliminated. One year I even "teased" it to sprout by watering my dead grass to see if anything would come up prior to overseeding. It did, so I sprayed the blasted grass again. For about a year or two after that, it appeared that I had finally won the battle, only to see it come creeping back again. I have now resigned myself to living with it, mowing high, fertilizing and watering on a regular basis. If you don't look closely, the lawn doesn't look too bad. What I have learned about this persistent grass is that the rhizomes have latent buds that become activated when the terminal buds or leaves are killed. About two weeks or so after killing off the leaves, the dormant buds begin growing. I could go on and on about our battling this pesky weed. If you are going to launch another attack on your lawn, now is the best time to do it because of the higher rate of translocation to the roots and rhizomes. Allow the grass to grow long and then apply a herbicide. When everything appears dead in a week or so, scalp mow and collect the clippings. Then lightly power rake, overseed and water. You just might get a leg up on the quack grass and enjoy a summer or two of it at least not being noticeable.
Q: I am writing to ask you about how to get rid of quackgrass. We had a new lawn put in a few years ago and now the quackgrass is showing up in spots and spreading. Weed killer labels usually list crabgrass but not quackgrass. Is there any correlation between the two? (Garrison, N.D.)
A: I do not think there is a correlation between the two except that both infect weak and thin lawns. There isnít a herbicide labeled for selective quackgrass control for cool-season grasses, so hand-weeding is an option in small areas. In larger areas with quackgrass spots, you may want to spot-treat with RoundUp, following the label's directions. Re-seed the dead spots with desired grasses. At times when the grass is not under consistent stress, such as spring and fall, lower the mowing height to about two inches. This will help prevent the quackgrass from spreading too fast without hurting the lawn grasses. If you have a large infestation, a complete renovation of the lawn may be necessary. In this case, make sure all the quackgrass is dead before you put down new seed.
Q: When should I be putting on crabgrass pre-emergent this spring? (Fargo, N.D.)
A: Crabgrass preventative is applied when the soil temperature is at 68 degrees or about the time the lilacs are coming into bloom in your neighborhood.
Q: My son lives in Minneapolis and he needs advice on how to kill quackgrass. It is starting to come in by his sidewalk and is spreading in the lawn. (Ashley, N.D.)
A: Unfortunately, there is no select way of eliminating quackgrass from turfgrass. In the sidewalk, just about anything can be used, with Roundup being the best choice. In turfgrass, the best approach is to maintain the lawn in a vigorous manner with regular irrigations and fertilizer and mowing at the high end of Kentucky bluegrass range, which is three inches or more.
Q: I have a lot of crab grass in my lawn along with other weeds. Will "Trimex Classic" take care of the crab grass and should it be applied? (E-mail reference)
A: It is unusual to see crabgrass in a lawn this early. Usually it doesnít make its presence known visually until late July or August since itís a warm season grass. It has simply been too cold and rainy for a lot of growth to take place. Could you be seeing quackgrass instead? Quackgrass enjoys this type of weather. You need to read the label to see what the herbicide takes care of since Iím not familiar with it and don't have a copy of the label in my office.
Q: What will happen if you fertilize your lawn with crabgrass preventer or Scott's turf builder and don't water it? Will it burn your lawn? When can you transplant an iris? My hosta leaves turned brown from frost in May. Can I cut them back? (E-mail reference)
A: Nothing will happen to your lawn because the material is "prilled" which means it will not activate until it rains or you provide irrigation. Most quality fertilizers have this or similar a treatment for just that reason. You are too late for the crabgrass preventer to be effective this year. Fall is the best time to transplant an iris. Yes, you can cut the hosta leaves back.
Q: We have a nice sod lawn but it is being invaded by quack grass from a vacant lot next to ours. Is there a way to get rid of the quack grass and not damage the good grass in the process? Are there any products that really work? (Hazen, N.D.)
A: How I wish! There is nothing that is legal that will selectively take quack out of bluegrass. Your best bet is to learn to live with it by keeping the lawn fertilized, watered, and mowed high (about three inches). Death, taxes and quack grass are the three irrefutable certainties of life!
Q: I was told when I purchased Trimec that it would not kill the grass, but it did. Will the creeping Jenny be back in the spring? How close can one spray to a hedge area and not kill it? How late in the fall can a person spray with Trimec? (E-mail reference)
A: I suppose TRIMEC could kill grass, but the label should have addressed that possibility. Perhaps the formulation was too strong? Whether or not the creeping Jenny will be back next spring depends on whether or not you got it before it dropped some seed. Fall is the best time for application, as the material is translocated better throughout the entire growing system of the plant. Since TRIMEC has soil activity, you had better stay away from the hedge to the point where you are not going to impact the root system, depending on the size and age of the hedge.
Q: I have a nasty infestation of crabgrass in my lawn. I took the advice under the lawn care extension web site and applied a pre-emergence crabgrass granular herbicide/fertilizer in early May. It definitely did not work and the crabgrass is flourishing. What can be sprayed on it now? The areas affected are twice as large as they were last year! (E-mail reference)
A: Don't fret, we can control the crabgrass of life! Here's what you can do now. The easiest approach is to try and find a combo product that claims both broadleaf and grassy weed control - post-emergence. There are products out there that contain both 2,4-D and MSMA or DSMA which will do the job. There are products like Acclaim and Dimension that may be difficult to find at this time which would also be effective. Culturally, mow high and don't overwater. Next spring, don't use the fertilizer/herbicide combo. The AI (active ingredient) is not high enough to do an effective job. Just use the straight pre-emergent material and fertilize your lawn later, around Memorial Day weekend.
Q: I have about 700 peonies that are overrun with quackgrass. Mulching helps, but the quack is persistent. Is there a herbicide for quackgrass in peonies? (E-mail reference)
A: There is nothing listed that is selective, only products like Finale and Roundup, neither of which are selective. If there is some way you can protect the peony plants while applying these herbicides, you may be able to bring it under better control.
Q: I have one flower bed with iris that has quackgrass in it. Can I use Roundup? Another flower bed on the north side has tulips and lilies in it plus lots of quack. I have tried Preen back there, but by the time the snow is all gone the quack has started to germinate. (Cooperstown, N.D.)
A: Roundup is a non-selective herbicide, killing anything it touches that is green and growing above the soil. It can be used safely over tulip bulbs since the foliage is not now present. You can "wick" the Roundup over the foliage of the quackgrass, keeping it carefully off the foliage of any desirable plants. Fall is the best time to do this.
Q: We recently built a new home, had several loads of black dirt hauled in and have a huge problem. We have not been able to get anything to grow but crabgrass. We have reseeded twice. We did spray the crabgrass (which had little effect); now our linden tree is dropping its leaves. We can only conclude that the soil must have been treated with some kind of herbicide. Can you help? (Watertown, S.D.)
A: Your information is too spotty: Did you backfill around the linden with these several loads of soil? If so, when did that take place? As little as 6 to 8 inches of soil over the rootzone of the linden could cause problems with survival. Crabgrass is an annual and easily controlled with a pre-emergent herbicide in the early spring. If you are going to be seeding your lawn, as opposed to sodding it, then you can only use a product called Tupersan (siduron). It is an effective annual grassy weed control that will allow the typical lawn grass seed to germinate. All other herbicides will prevent the lawn grasses from germinating for up to 12 weeks. It could well be that the topsoil came from a former wheat field where broad-leaf herbicides were heavily used. If so, then the residue could be migrating to the roots of the linden and being taken up and gradually killing it. To test the soil, try growing a bean or tomato plant in it. If either die, that is likely the problem. The only options open to you then are the complete removal of the soil you brought in or generous incorporation of activated charcoal into the soil to absorb the herbicide.
A: Violets are tough to control. Ask your lawn care professionals to get Confront. This is the most effective broadleaf weed control product I have seen on the market for turfgrass use. Don't go out and spend $100 for Turflon when the lawn care operator can get the Confront product. This fall would be an ideal time for application.
A: The reason you are not finding any information is because there is no selective control available. However, I doubt that you are having a quackgrass problem. Sod growers are fastidious about preparing their soil and making sure there are no rhizomatous weedy grasses or broadleaf weeds in the soil they are intending to use as sod. I would more likely think it is a case of misidentification, and is an annual grass, like crabgrass or one of the foxtails. These often come up between the seams of the sod the first year. Control of these grasses is easily accomplished with any number of pre-emergence products on the market. If you would like me to make a positive identification of the weed, please send it to me, in a ziploc bag ( don't add moisture) showing as much of the plant as possible.
A: Best approach is to get a power rake or lawn dethatcher and run it over the bare areas to scarify the soil. Broadcast more seed, and topdress with a wood-fiber mulch that will help hold it in place and extend the effects of rain or irrigation. Weeds will be a problem, but they can be beaten with persistence. Once you have enough grass to mow, you can then attack the weeds with the appropriate herbicide. Hang in there! A year from now this will be a memory hardly worth recalling.
A: Roundup, carefully applied, will do the trick. I would go back to the source of the seed and leave a piece of my mind, though, if you are sure that the source of all the quack is from the purchased seed. If the seed came in a sealed container and had a current seed label that stated the species and variety, purity and germination and listed no noxious weeds, you have a case for reimbursement, at least for the purchase price.
A: I suggest trying a major rental store to see if they should have a seeder, but I doubt it. You may have to hire it done by a lawn service company. If that option cannot be found, I know it will work if you do the following: After everything has been killed off, scalp mow the entire lawn, collecting the clippings. Go over the area in two directions, perpendicular to each other, with a power rake. Spread the seed with a drop or cyclone spreader Drag in the seed with the back of a leaf rake or a piece of chain-link fence. I've done it several times with great success. The power rake is easier to find than the slit seeder.
Q: I was told that there is a pre-emergent herbicide for crabgrass and quackgrass. If so, will it kill the rest of my lawn? (Mohall, N.D.)
A: There are pre-emergent products available to kill crabgrass, an annual that appears in lawns beginning midsummer. These include products with chemicals in them such as trifluralin or pendamethalin. There shouldn't be any problems with the pre-emergent killing your lawn unless you are seeding it, because it only disrupts seedling germination.
Quackgrass, on the other hand, is a little more difficult to control because it doesn't spread by seeds like crabgrass, but instead, by its underground rhizomes. Post-emergent herbicides such as Vantage should be applied by spot spraying directly to the quackgrass.
Q: Can a person put crabgrass preventer on in the spring over a piece of ground that has been sown with grass? Also, can I spray Roundup over tulips and lilies that are not up so I can kill quackgrass? (e-mail)
A: There is only one pre-emergent crabgrass herbicide that can be used that way -- Tupersan (Siduron). All others will take out the desired turfgrass seed as well. Roundup is deactivated as soon as it hits the soil. As long as there is not green showing above ground, the tulips will be safe.
Q: I think my lawn is plagued by ground ivy, but I also need to know how to get rid of it. I also have some plant that has bluish purple star-shaped flowers that I would like to get rid of.
Is crabgrass best treated with spray or pellet chemical treatment, and is fall the best time for treatment? (e-mail)
A: Ground ivy will take a couple of applications of Trimec to control it. The same chemical will also take care of the violets -- the purple flowers.
Crabgrass should be dead now from the frosts. Being an annual, it is best controlled by a pre-emergent herbicide in the early spring.
Q: I am looking for something to spray quackgrass with to kill it. I heard someone talking about a chemical called Casoron 4G. Could I use it in my flowerbed? (Cando, N.D.)
A: Actually there are a couple of quackgrass killers out there that can be used: Casoron and Vantage, a postemergence. The list for acceptable crops is quite extensive, so I encourage the reading of label direction before using.
Roundup can also be used on quack infestations. The lawn and garden formulations come in handy spray bottles that allow close application of the product near desirable plants. You might want to isolate the source of crabgrass. If it is coming in from the surrounding turf area, a physical barrier in the soil will be needed to keep it form re-invading.
Most elevators should have these products for sale. If not, then try a garden center.
Q: Enclosed is a plant that has recently invaded my lawn. Can you identify it and tell me how to get rid of it? (Fargo, N.D.)
A: You sent me a perfect sample of crabgrass! This is a warm-season annual that is killed off with fall frostsbut not until it has dropped thousands of seeds. Next spring, just as the forsythia flowers are fading (or the lilacs just opening) apply a preemergent product like Dimensionģ for control. Then, do everything possible to grow healthy, vigorous grass: fertilize, water, and mow regularlydoing so at 2Ĺ to 3 inches. This should keep this pest from making a comeback!
Q: I hope you have some ideas about what I can do with a row of Golden Currant shrubs that we planted along our front yard (250 feet) three years ago. We didn't know anything about this shrub when it was planted, but now I'm afraid it's going to be too "high maintenance" to keep looking nice. Unfortunately, we did not have landscaping fabric put down when the shrubs were planted, and now it is impossible to keep them weed- and quack-grass-free. I weeded each plant this spring, but the quack grass is still coming. Also, there are so many small branches to weed around. Could we spray Roundup or Spectracide around the base of these shrubs after the first killing frost this fall? Would it help much to put landscaping fabric between each shrub now? We also thought about putting tree mulch or grass clippings at the base of each shrub, in an attempt to choke out the weeds and quack grass. Do you have any advice on when and how to trim/prune these shrubs? We're considering replacing all these shrubs with a more manageable planting of cottoneaster, especially because of the location in our yard.
A: Bad news! Quack grass is tough to keep in check. It would likely grow through or around the landscape fabric.
If you are unhappy with your currants, get them out as soon as possible and spray the entire area with Roundup to kill off the quack. Replant this fall with the cotoneaster.
Q. At what soil temperature will crabgrass germinate and how do I control the crabgrass? (Oakes, N.D.)
A. When the soil temperature is around 55 to 60 F at a depth of 2 to 3 inches, crabgrass seed (some of it) will begin to germinate. If you use Dimension and crabgrass preventer, you will get 16 weeks of control. This is a good feature because crabgrass seed, as you know, doesn't germinate all at once, but throughout the season. This product will take you through August. Anything that sprouts after that will get toasted by fall frosts before seed can be set.
Thanks for writing.
Q. We are wondering what this grass is that has invaded our lawn in a few areas. Also, what can be done to get rid of it--besides digging it up by hand. It grows low to the ground and spreads out very readily. We read the articles all the time. Thank you. (Litchville, N.D.)
A. Your lawn is being invaded by an annual grass known as crabgrass. The best defense for this is a healthy, dense turfgrass.
I suggest an application of Pre-M (preemergent grassy weed control product) about the time the lilacs come into bloom. You also need to become aggressive in rejuvenating your lawn: fertilize, mow at three inches and as needed, water to keep the grass from going dormant, and reseed the bare spots.
Q. I would like to start a perennial garden this fall. What can I do to stop quackgrass from growing into it in a few years. Would using railroad ties filled with dirt help to keep it out? (Tappen, N.D.)
A. Yes, railroad ties would help, but they are a lot of work. It would be better to use landscape edging that you can push into the soil about 4 to 6 inches deep. This is usually deep enough to keep quack rhizomes from invading.
Q. I have enclosed a few leaves from a winter hardy Lillian Gibson rose. Three years ago the new spring growth froze off following a cold snap. Since that time the plant has become smaller in size and the leaves will turn yellow and fall off. It had just a few blooms this year and once again the leaves fell off. Also, thanks to one of your Hortiscope columns in the Farm Forum pages, I have been able to locate a pre-emergent without purchasing a lawn fertilizer combo for crabgrass. Will the seed of crabgrass be fertile when it continues to form a head after being sprayed with Roundup or Trimec? Thanks for your help. (Mitchell, S.D.)
A. I have just one concern--Trimec and Roundup are not pre-emergent herbicides and are not used in the control of crabgrass. Several pre-emergents are available: Pre-Em, Tupersan and Dimension. All are applied in the early spring around lilac blooming time. Concerning the crabgrass, the answer is yes. The plant is killed, but not the seed. Your rose sample has a bad case of black spot, Diploearpan rosae, a fungus disease brought on by high humidity and splashing water. Several fungicides are available for control. Look for something with chlorothalinol or triforine. Application should be made as new growth emerges--every 10 days or so. Also, avoid spraying water on the leaves. After pruning back in the spring while the plant is still dormant, spray the canes with lime-sulfur for sanitization.
Q. I always read the write-up you have on plants in the Weekly Peddler, but somehow I missed the one on quackgrass in iris. This is a regular pain for me as I have a lot of them. Could you please send me some information on this matter.
Your write-ups are welcome to those of us who need help. Keep them up. (Lakota, N.D.)
A. Quackgrass in iris can be a real problem, in that I have found the rhizomes of the quackgrass can penetrate through the stout rhizomes of the iris.
My suggestion is not widely embraced by many gardeners, but if you are wishing to grow those iris where they are, you must be determined in your attack on this obnoxious weed. Here it is:
1.Carefully dig out the entire iris planting. Discard any rhizomes that have been penetrated by quackgrass.
2.Going down 4 to 6 inches, remove every quackgrass rhizome you can find. Be sure there are no quack rhizomes along the border of your planting bed. They will only reinvade once the iris are reset.
3.Once you are sure the area is clean, reset the iris and keep future invasions to a minimum with carefully sprayed Roundup.
Q. I would like to know how to get rid of quackgrass in my raspberry patch.
I enjoy reading your articles. (Rutland, N.D.)
A.Quackgrass in raspberry patches can be controlled with Roundup, if the canes are dormant, in late fall or early spring before new growth begins.
It can also be controlled selectively with a material known as Poast or another one called Casoron. Don't be discouraged quackgrass is difficult to control and may take a couple of applications to completely control.
Q: I planted a large area of new lawn last fall, including an area where a new shelter belt is planted. The grass is coming up but so are the weeds. In some areas there is shepherd's purse growing so thick that I am sure it is competing too much with the grass. What can I do about the weeds? There are too many to pull out by hand. At what point can I apply a broadleaf weed killer? Do I need to fertilize the new lawn this spring? Every year I put down pre-emergent crabgrass herbicide, and every year I have tons of crabgrass. I will try again this year, but would like to know when I should put it down. Can you give me an approximate date? Is it OK to cut potentillas way down, maybe a foot above the ground? I have some that seem so overgrown. I am planting dahlias in my garden for the first time this year. Can I plant them now or do I need to wait until the frost free date? Sorry I have so many questions, but it seems like every time I go outside, I think of something else! (Fargo, N.D.,e-mail)
A: You can apply the broadleaf weed herbicide to your new lawn when the weeds are actively growing. It is best to get them in the juvenile stage, as control is much more effective. It would do the lawn good to receive some fertilizer this spring about mid-May. Are you sure you are fighting crabgrass and not quackgrass? Many people get the two turned around. In many weed-and-feed products on the market, the concentration of the herbicide is usually lower than it is when purchased straight without any fertilizer included. The active ingredient (AI) in crabgrass control products is usually pendimethalin or oxadiazon, and in some cases, siduron. All of these are pre-emergence materials that have to be applied BEFORE germination takes place. Another point of confusion for consumers is the fact that some weed-and-feed combinations go after the broadleaf weeds, such as dandelion and broadleaf plantain, and are post-emergence materials that are effective only AFTER the weeds have emerged. Neither of these has any effect on quackgrass, which is a cool-season, rhizomateous, perennial grass. There is no selective product on the market for controlling this weed. Crabgrass starts germination about the time the lilacs are beginning to bloom. Any pre-emergence herbicide needs to be applied just prior to that time, or about when the forsythia stop blooming in your area. Yes, cut the potentilla back as far as possible. We did it to ours this year, as they have just become a tangle of unattractive branches. Better to have attractive fresh-looking foliage and growth rather than something that looks like it was used for mortar practice! With the arrival of May, I would say you can put your dahlias out anytime now. Just keep an eye to the weather, in case a cold snap hits and the tubers have begun to emerge succulent growth. Just toss a sheet or newspaper over the new growth.
Q: I think there is quackgrass growing in my lawn, but it seems much finer than regular quackgrass. Could you please let us know what kind of grass it is? (Campbell, Minn.)
A: I can tell you for certain that it is not quackgrass. My best guess is that it could be either Sandburg or Canada bluegrass.
Q: What would you recommend to get rid of crab grass in a big farm yard? It would be quite expensive to use preemergent type products with the fertilizer and crab grass prevention products together. Is there any product you would recommend that would work for us. We have heard of "Drive" and wonder how it would work and also what affect it would have on the trees and flowers which are part of this large yard. (E-mail reference, Cavour, S.D.)
A: I'm sorry, but I don't know what Drive is, what the active ingredient is, or what crop(s) it is labelled for. Consequently, I cannot make any recommendations on that product. I do know that there are plenty of other stand alone products that can be used in turfgrass to control crabgrass as well as other annual grasses. They include the old standbys like pendimethalin, Tupersan, Dacthal, and Betasan and new intros like Acclaim and Dimension. I do agree with you 100 percent that combo products are not as effective, mostly because the active ingredient is too low for heavy infestations. Apply the herbicide separately from the fertilizer.
Q: Can you identify the enclosed weed and tell me how to get rid of it? It is invading the yard and the garden. It lays very flat to the ground and quickly takes over the area. (Cogswell, N.D.)
A: You have sent me one of the most beautiful samples of large crabgrass - Digitaria sanguinalis - I have ever seen! So good in fact, that Iím having it mounted to show to my future turfgrass management classes. It is best controlled with a pre-emergent herbicide in the spring about the time lilacs are in bloom. There are several products labeled for grassy annual weed control. Make sure the one you pick contains pendimethalin. Do not use a weed and feed product. The concentration is not strong enough to be very effective.
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