To celebrate National Invasive Species Awareness Week we are going to highlight invasive species that affect the basin and range.
In today's post, we meet Medusahead (Taeniatherum caput-medusae). There are several reasons I chose to start with medusahead. While it is a growing problem throughout the Great Basin, I hadn't been exposed to it until I worked to control it in Paradise Valley in the summer of 2011. Also, above our home near Reno it is taking over vast slopes of the Sierra foothills. Its dense carpets suffocate all other growth and when a thick patch is encountered while hiking, it's easy to see the danger to native wildlife and the health of the ecosystem it presents.
Medusahead originates from Eurasia and is thought to have made its way the US in the late 1800s. It is an annual grass that reproduces by seed. It is a slender-looking grass that can be from 0.5 to 2 feet tall. The seedheads form a spike and have awns that are up to 3 inches in length. The long awns are straight and compressed when green, but, upon drying, they twist and spread becoming reminiscent of the snakes atop the head of the mythic Medusa.
One of the recognition clues in identifying medusahead is its coloration. Medusahead typically matures weeks later than most annual grasses, which tends to create islands of green in a sea of dried, brown grass. Also, once they die, the plants bleach to a light tan color that appears lighter than the surrounding dead grasses. Another clue is that the seedhead spike does not break apart easily as the seeds mature--as they do with foxtail and squirrel tail, two species that are often mistaken for medusahead.
Medusahead grows best on clay soils and primarily infests disturbed land. It is known to occur in Nevada in Churchill, Douglas, Elko, Humboldt, Pershing, Storey and Washoe counties. It is unpalatable to grazing animals due to the high levels of silica in both the foliage and the long, barbed awns.
According to the Nevada Noxious Weed Field Guide, tillage, mowing or grazing prior to going to seed can reduce stands. Burning has had mixed results; but is most effective with a hot, slow fire prior to seed maturity but after other species have dried out. Burning can also be used to reduce the thatch layer. As for pesticides, best results have been made with the application of imazapic or sulfometuron before emergence or to small, actively growing plants and glyposate to actively growing plants. Check with a certified herbicide applicator to get current information on pesticide use.
California Invasive Plant Council, "Medusahead entry," accessed 2-27-2012, see entry here.
Creech, Earl, Schultz, Brad and Blecker, Lisa. Nevada Noxious Weed Field Guide. University of Nevada Cooperative Extension, 2010. PDF available here.
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