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Quackgrass illustration

Quackgrass

(extremely noxious weed - Elytrigia repens)

Quackgrass (also known as: couch, quitch, devils, wheat, scutch, twitch, witch, dog or durfa grass) are undesirable perennial grasses that grow as weeds in many lawns. Unfortunately there is no herbicide you can use that will not also kill the desirable lawn grasses.

Identifying Characteristics

A perennial grass weed with auricles that clasp the stem, rhizomes, and a long, narrow spike for a seed head. The auricles of this weed helps to immediately distinguish it from most other grass weeds, however tall fescue (Festuca arundinacea), Annual Ryegrass (Lolium multiflorum), and perennial ryegrass (Lolium perenne) are similar grasses that also have auricles. However, none of these grass weeds have rhizomes like quackgrass.

Quackgrass

Controlling quackgrass

An understanding of how the quackgrass grows will help avoid common errors in battling this plant. Quackgrass grows from underground rhizomes to an unmowed height of 1' - 4'.

It has thin, flat, bright ashy green leaf blades. The seed spike grows from 3" - 8" long and appears in July. Quackgrass seed is often found in rye straw, so you may want to avoid using this as mulch in your garden. Each quackgrass plant produces about 25 seeds and they remain viable 3 - 5 years in the soil. It takes 2 - 3 months for a newly germinated plant to develop rhizomes. It is very important to eliminate the plants before they reach this stage.

The creeping rhizomes are so tough they can grow through a potato tuber, or push up through asphalt pavement. If left to grow, they will form a dense mat 4" thick in the upper part of the soil. One plant can produce 300' of rhizomes each year. Never rototill where quackgrass is growing. The rototilling will chop up the rhizomes and create thousands of new plants.

Quackgrass produces many underground stems, called rhizomes, that are almost impossible to remove by digging. Broken pieces of rhizomes left in the soil will sprout to make more Quackgrass plants. One method of controlling Bentgrass and Quackgrass is to apply a herbicide that contains the active ingredient glyphosate. These herbicides are sold as Round Up or Kleen Up. Be aware that glyphosate kills desirable grasses as well as weeds. Apply the herbicide only on the Bentgrass and Quackgrass patches.

Apply glyphosate in spring or fall when the grasses are actively growing. Wait approximately seven days, then reseed or sod the area. If you decide to till the soil prior to establishment, and see bits of Quackgrass rhizomes coming to the surface, remove these. Or wait 2 weeks or so until enough new Quackgrass leaves emerge and kill the new plants with a second application of glyphosate.

An alternative method is to mow the lawn-wait 3 - 4 days, then wipe the glyphosate onto the taller growing Quackgrass with a paint brush, sponge mop or applicator. Be sure to read and follow label directions.

One problem with using glyphosate on quackgrass is that up to 95% of the lateral buds on the rhizomes are dormant even though the plant is actively growing. Since herbicides are translocated from the leaves to actively growing plant tissue, after about 7 days the glyphosate degrades and the dormant lateral buds will start to grow new shoots. It may take more than one application to completely eradicate quackgrass.

One way to overcome lateral bud dormancy is to apply nitrogen fertilizer. This will break lateral bud dormancy, and the herbicide will be translocated to the now actively growing plant tissue and kill the entire plant. Repeat the application of glyphosate every 30 - 45 days; avoid cultivation for 2 weeks after each application.

In daylily beds or other perennial flower beds quackgrass can be very difficult to control. You will need to use a small applicator like a child's paint brush or small sponge, then be extremely careful to apply the herbicide only to the quackgrass leaves. If you contact the daylily leaves with glyphosate, it can kill them, too.

In perennial gardens, a selective systemic herbicide containing fluazifop (fusilade) (Ortho-Grass-B-Gon) can also be used successfully. It is important to 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 12 months after application), rhubarb, spinach, garlic, peppers, onions and non- bearing trees and vines. Grass-B-Gon is best applied to young quackgrass plants with 2 - 4 leaves; two applications are sometimes required to completely eradicate quackgrass. Apply this herbicide when no rainfall is expected for 24 - 48 hours.

Quackgrass summary:

  • Cool season perennial weed

  • Patch forming, coarse textured grass that spreads by while, long-lived rhizomes.

  • If unmown, quackgrass can grow to 4' tall.

  • Quackgrass root system is fibrous

  • Quackgrass blades are flat, dull green to light blue-green and taper to a point.

  • Quackgrass is an aggressive grassy weed and found in many lawns throughout the growing season, especially during cool weather in both spring and fall.

  • Can be controlled by pulling the weed or by using a non-selective herbicide such as Round-up