Your cheatin' grass… will tell on you…

Cheatgrass is having a spectacular year in northern Larimer County. The extremely wet fall associated with last year’s floods led to a tremendous germination of seeds that may have been in the seedbank for years. Our wet spring helped many of these plants to mature and produce seed. You have probably seen patches of purple and brown in a previously green pasture or hayfield, experienced socks full of prickly seeds or dogs with seeds in their coat or paws. Where did this irritating plant come from? And more importantly, what can we do about it?

Ellen Nelson
Larimer County Weed District

Cheatgrass arrived from Europe as a contaminant in grain in the 1800s. It was also used as packing material as settlers moved west. It spreads easily in the coats of animals, and along railways and roads. Cheatgrass is a winter annual, germinating and starting to grow in fall. Over-wintering as a seedling, it “cheats” by getting a head start the following spring. With this head start and rapid growth it outcompetes native vegetation. Cheatgrass produces seeds, then goes dormant early in the growing season. At this point it is mostly fine, dry fuel that can lead to increased fire danger. This fire cycle can perpetuate cheatgrass, making it difficult to re-establish native vegetation.

Fortunately, there are actions you can take to combat this invasive weed. Some herbicides are effective at low rates when applied at specific phases of the cheatgrass lifecycle. The ideal time to apply herbicide is the end of August into September, when cheatgrass begins to germinate. The Larimer County Weed District has done field trials and found that Plateau or Panoramic applied at 4 to 6 ounces per acre at this time can reduce the amount of cheatgrass that germinates. This is an example of when it is very important to calibrate your spraying equipment, because over applying these herbicides can affect native grasses. These herbicides have a residual effect that can kill germinating seedlings for several months. It may be advantageous to remove the previous year’s dried up old growth to allow the herbicide to contact the ground and cheatgrass seedlings present.

Many perennial grasses compete well with cheatgrass. Often, eliminating the fall flush of cheatgrass is sufficient to release native perennial grasses for a resurgence of native vegetation. Some of the native grasses that reappear when cheatgrass is removed are western wheat, blue grama, sideoats grama, needle-and-thread grass, green needle grass and more. When reseeding with native grasses, consider the species listed above. It is wise to wait a year to reseed after applying these herbicides, because of their residual effect.

There is an ongoing debate about reseeding with non-native grasses, especially if they can outcompete cheatgrass more effectively than some of the native grasses. Several cultivars of crested wheatgrass have been shown to compete with cheatgrass, and while not a native grass, it provides more forage, less fire danger and an opportunity for improved range and pasture compared to a monoculture of cheatgrass.

For more information on weeds, weed identification, pasture management, reseeding, herbicide recommendations, and free site visits please contact the Larimer County Weed district at 970-498-5768.

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