How to Kill Quackgrass

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What is Quackgrass? 

Quackgrass is a nasty grass weed that, if left untreated, can take over your lawn or garden quickly. Quackgrass is its most common name, but it may also be called couch, quitch, devils, wheat, scotch, twitch, witch, dog or durfa grass. Quackgrass has thin, flat, bright ashy green leaf blades. It is a perennial grass weed with auricles that clasp the stem, rhizomes, and a long, narrow spiked seed head. This seed head grows from 3 to 8 inches long and appears in July. Quackgrass grows from underground rhizomes (or stems) that lie dormant in the winter and pop back up in the spring. If left uncut, these stems can grow from 1 to 4 feet high.

Containing Quackgrass

Quackgrass is hard to contain, because you can only use herbicides on it that will not kill your lawn along with it. It is also tricky to treat because of the rhizomes. They are very strong and can even grow through pavement. It is important to try to kill the plants before they get to the rhizome stage (it should be treated in its youngest stage, in the first 2 to 3 months before the plant matures enough to create the stems). Each quackgrass plant can grow up to 300 feet of rhizomes each year. These rhizomes can be dug up, but it is a very difficult and tedious process. You should also never chop up or till the rhizomes because the small, chopped up pieces will multiply into new plants.

Each quackgrass stem will produce 25 seeds each year, and these seeds can live up to 3 to 5 years in the soil. Before herbicides were invented, farmers with outbreaks of quackgrass would clear out the field and leave it empty for up to two years, and kill all of the weeds to make sure there were none left to kill their crops. Now weed killers are strong enough to wipe out the annoying weed without waiting.

Eliminating Quackgrass

The chemical of choice to kill off the grass is glyphosate. This common weed killer is found in products like Round Up or Kleen Up. If you use these herbicides, be aware that it will kill any grass it touches, so it is very critical to apply it with a paintbrush or a small applicator that you can control easily. If the outbreak is large, you can always kill the whole yard and start over fresh, after you are sure the rhizomes are dead. It is also recommended to treat the plants in the spring or fall, when the grass is actively growing. Then wait to see if more seeds are germinated before reapplying the herbicide a few weeks later to kill off any new growth. You can also cut your lawn short and wait for the quackgrass to grow for a few days, (it grows faster) and then apply the weed killer to the quackgrass alone. You will know which stalks are quackgrass because they will be taller.

Maintaining Control

Another problem associated with killing off the weed is that up to 95% of the lateral buds on the rhizomes are dormant, even though the plant is growing. This is a problem because herbicides cannot kill the dormant parts of the plants. Therefore, a week later when the glyphosate wears off, the buds can awaken and start to grow new shoots. It is important to treat the weeds again. One way to counter act this problem is to apply nitrogen fertilizer to the weeds. This will break the lateral bud dormancy by awakening the buds, so that the glyphosate can kill the entire plant. Repeat the application process again in 30 to 45 days and make sure to avoid cultivation of the soil for 2 weeks after each application.

If the quackgrass is located in a flower, herb, or vegetable garden, you can do a similar treatment, but use a selective systemic herbicide containing fluazifop (fusilade) (Ortho-Grass-B-Gon). Apply this only to the quackgrass leaves as it may damage or kill all monocots (daylilies, iris, gladiolus, lilies) once it contacts the leaves. This product can also be used with asparagus (non-bearing plants only; you cannot harvest for 1 year after application), rhubarb, spinach, garlic, peppers, onions and non- bearing trees and vines. Grass-B-Gon is best applied to immature plants with 2 to 4 leaves; two applications are sometimes required to completely eradicate quackgrass. Do not apply this if rain is in the forecast within the next 48 hours. Make sure when applying any treatments that the temperature is above 50 degrees.

To avoid future breakouts of the weed, cut your grass frequently. Catch all outbreaks quickly, before the rhizomes grow and take over your yard or garden. Your time will be lush and healthy in no time at all with a little care.

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