How long are cheatgrass seeds viable?

Question answered by Kristin Kaiser, Plant Ecologist INL ESER Program

Figure 1: Cheatgrass (Bromus tectorum) in mid-July after it has produced seed and is now dead standing plant material found in the Snake River Plain of southeastern Idaho. Photo Credit: Kristin Kaser

Cheatgrass (Bromus tectorum L.) is a highly invasive introduced winter annual. It has several common names like downy brome, June grass, and others that vary within cultural regions. The plant’s scientific name roughly translates to “brome of the roofs” which references Europeans who used it as thatch. Cheatgrass is native to the Mediterranean, and made its way to North America in the late 1800’s through impure crop seed, packaging materials, boats, etc. By the 1930’s, it had established itself in western rangelands, near agricultural fields, and close to homestead establishments. In Aldo Leopold’s “A Sand County Almanac” he states, “… the spread was often so rapid as to escape recording; one simply woke up one fine spring to find the range dominated by a new weed.”

Cheatgrass has special adaptations which allow it to outcompete the native plants of Idaho. Cheatgrass is a winter annual and typically germinates in the fall, but under ideal conditions can also germinate in winter or spring. The seedlings mature faster and produce viable seed earlier in the growing season than most native plants and deplete soil moisture before native seedlings can become established. Although the seed is viable for only two to three years, due to its jumpstart nature and massive seed production, it will quickly outpace native plants, especially in disturbed ecosystems. In addition, cheatgrass can form dense stands that provide fine textured fuel for wildland fires. As the West becomes heavily invaded by cheatgrass, fire regimes increase in frequency. Native perennial plants do not recover as quickly and are slowly removed from the system with each wildland fire. The loss of natives negatively impacts a healthy ecosystem as many animals depend on the high-quality forage of native plants.
Mack, R. N. (1981). Invasion of Bromus tectorum L. into western North America: an ecological chronicle. Agro-ecosystems, 7(2), 145-165.

Cheatgrass Seed Dispersal

Cheatgrass has long awns on its seedhead which attach to nearly everything they it touches. By sticking to other objects the seed is transported to other areas, starting new infestations.
Many people use outdoor areas for work and enjoyment. If you like to picnic or hike in the forest or walk your dog in a park, you have the potential to spread cheatgrass and other noxious weeds.

A Sticky Situation

Materials: ball of yarn, 10 or more friends

  1. Think of some activities that someone might do outside. For example, you may list hiking, camping, picking berries, birdwatching, walking your dog, ATV riding or boating.
  2. Assign 3 friends to be cheatgrass seeds and have them stand in a group in the middle of the playing area. Tell them that cheatgrass seeds are very sticky and they will need to have grab any yarn that touches them.
  3. Ask all of the other friends to form a circle around the cheatgrass.
  4. Give the ball of yarn to a friend in the circle.
  5. Holding the end of the yarn, tell them to name an activity they like to do outside and then toss the ball of yarn to someone else in the circle.
  6. If the ball of yarn hits the Cheatgrass during the toss, it is stuck there and the Cheatgrass plant that caught the yarn can choose who to give it to next.
  7. Repeat Steps 5 and 6 until everyone has a turn. Did you make a web of yarn? How many times did the yarn touch the cheatgrass?
    Each time the yarn touched the cheatgrass represents how easy it is to pick up the cheatgrass seeds on your clothing and spread the cheatgrass to another area.
    When you’re playing outside and you get cheatgrass on your clothing, make sure to throw the weed seeds in the trash. Don’t throw them on the ground. You don’t want to start a new infestation.

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