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United States Department of Agriculture

Agricultural Research Service

Title: Annual Wheatgrass: a New Look at An Old Invasive Range Weed

Authors
item Young, James
item Clements, Darin

Submitted to: Rangelands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 20, 2004
Publication Date: February 15, 2005
Citation: Young, J.A., Clements, C.D. 2005. Annual Wheatgrass: A new look at an old invasive range weed. Rangelands. 27(1):1-5.

Interpretive Summary: There are many well known invasive annual weed species on sagebrush/bunchgrass and salt desert ranges of the Intermountain Area of the Western United States. Cheatgrass, medusahead, and Russian thistle are among them. Annual wheatgrass (Eremopyrum triticeum) is not a so well known species. The 1935 edition of A. S. Hitchcock's Manual of Grasses of the United States lists this species as Agropyron triticeum. At the same time Sergel Nevskii, a senior agrostologist at the Botanical Institute of the Academy of Sciences of the USSR published that annual wheatgrass was not Agropuron, but belonged to the genus Eremopyrum. In the volume of the Flora Europaea, the characteristics used to separate the genera Agropyron and Eremopyrum are: 1) the glume of the latter are joined at the base, 2) the rachis, or axis of the spike, of Agropyron does not disarticulate or fall apart at maturity, and 3)the Agropyron are perennials and the Eremopyrum are annuals. Many resource managers refer to annual wheatgrass as annual crested wheatgrass, but it is not a crested wheatgrass. Annual wheatgrass seedlings can be confused with the more abundant cheatgrass, but when they mature, annual wheatgrass is distinctively different from cheatgrass as the bracts are tightly held as a wheatgrass characteristic. After maturity annual wheatgrass essentially disappears as the sparse leaves fall closely to the ground, whereas cheatgrass herbage is upright. The ecological importance of annual wheatgrass is that it illistrates that each seral stage in the continuum from Russian thistle and halogeton to exotic annual grass dominance is not a single species dominance, but rather a true continuum of assemblages of species that can be broadened or made diverse by new introductions.

Technical Abstract: Annual wheatgrass (Eremopyrum triticeum) is native to Russia. Formerly referred to as annual crested wheatgrass (Agropyron triticeum), annual wheatgrass is not a crested wheatgrass. Annual wheatgrass seedlings can appear to be that of the widely known annual weed cheatgrass (Bromus tectorum), but cheatgrass leaves are wider and with the ability to germinate in the fall, leaves often have a reddish color to them from insufficient nitrogen availability. As annual wheatgrass matures it becomes very distinctive as the seed heads have the wheatgrass characteristic. The spike is extremely compact with the florets set perpendicular to the central axis or rachis. Preliminary germination experiments in the Wildland Seed Laboratory, USDA-ARS, Reno, Nevada suggests that annual wheatgrass is at least equal to the germination potentials of the well known invasive annual weed cheatgrass as it also germinates at very cold and cold seedbed temperatures. Our extensive surveys of the rangelands of northern Nevada have identified the transition zone between Wyoming big sagebrush and salt desert plant communities as the key environments for locating annual wheatgrass infestations. The ecological importance of annual wheatgrass is that it illustrates that each seral stage in the continuum from Russian thistle and halogeton to exotic annual grass dominance is not a definite single species dominance position, but a true continuum of assemblages of species that can be broadened or made more diverse by new introductions

Last Modified: 10/1/2014
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