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A Pacific Northwest Extension Publication Oregon State University, Washington State University, University of Idaho Tuber Oatgrass PNW 445 March 1993 J.P. Fitzsimmons and L.C. Burrill Do you want to print a copy? We recommend downloading the print version (96 K). First download the free Adobe Reader, if you don't already have it. Contents Identification Related Species Control Tuber oatgrass (Arrhenatherum elatius var bulbosum) is native to Europe and was introduced into this country as a meadow grass. It is found throughout the Pacific Northwest but is common west of the Cascades and locally in central Washington. Tuber oatgrass concentrates in pastures, roadsides, non-crop areas, and cultivated fields. It spreads by rhizomes that produce a new, bulb-like structure called a corm at the bud. Each new corm may form groups of four to five corms on top of one another. These corms each have a regenerative bud and not all corms sprout in a given year. Buds on new corms usually remain dormant as long as the shoots are alive. Aerial shoots develop in the autumn, growing rapidly in the spring, and withering in the fall. Seed shatters at maturity, is not dormant, and has a high germination percentage. Tuber oatgrass is not considered noxious in Idaho, Oregon, or Washington. top Identification Tuber oatgrass is a creeping perennial grass that may reach 6 feet tall and forms strings of corms at the base of the stem. Newly formed corms are small and white. As the season progresses, corms become larger and turn brown when mature. Occasionally, green corms form above ground. The leaf blades are flattened, rough, and 3/8-inch wide or less. Sheaths are open. Ligules are short and membranous. The panicle is 1/2 to 1 foot long, and narrow with short, whorled branches with spike-lets forming to the base. Spikelets are 5/8-inch long, each spikelet with two florets. The lower floret is awned from the back of the lemma, and the awn usually is bent.   Figure 1--Tuber oatgrass and tall oatgrass look alike above ground. Figure 2.--Stacked corms are unique to tuber oatgrass Related Species Tall oatgrass (Arrhenatherum elatius L. var elatius) differs from tuber oatgrass in that it has no corms. Plants do not spread by rhizomes, rather they grow in tufts. This plant also was imported from Europe and is used as a pasture grass. It is a common grass along roadsides in northern Idaho, eastern Washington, and northeastern Oregon. top Control Mechanical. Infrequent tillage may spread tuber oatgrass more than control it. Tillage breaks groups of corms and spreads them throughout the field. One corm can produce over 300 new corms per year. Corms brought to the surface dry and die, so monthly tillage throughout the dry season may lower the populations. Chemical. Several herbicides can control plants that have emerged and are growing well. However, a single herbicide application has a limited effect against an established stand of tuber oatgrass because many corms do not produce leaves each year. This dormancy allows corms to escape control and to sprout and spread the next year. The best time to apply systemic herbicides is when the plant sugars are moving into the storage area, around May 1. Limited control is seen when the plants are sprayed in the fall after regrowth has occurred. Glyphosate is effective against the emerged plants at the six- to seven-leaf stage. Herbicide registrations change frequently; therefore, this publication does not contain specific herbicide use instructions. Registered uses are summarized each year in the Pacific Northwest Weed Control Handbook. In addition, detailed instructions for herbicide use are provided on herbicide container labels and in other literature provided by herbicide manufacturers. Use Pesticides Safely! Wear protective clothing and sefety devices as recommended on the label. Bathe or shower after each use. Read the pesticide label--even if you've used the pesticed before. Follow closely the instructions on the label (and any other directions you have). Be cautious when you apply pesticedes. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use. top Prepared by Jim P. Fitzsimmins, graduate student, crop and soil sciences; and Larry C. Burrill, Extension weed specialist, Oregon State University. March 1993.

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