Tom's Blog

Sunday, June 12, 2011

Reed canary grass at upland sites

Reed canary grass (Phalaris arundinacea) is an ecologically invasive grass that causes great problems in wetland sites. It is one of the most widely occurring weeds and is exceedingly difficult to control. It is a prolific seed producer, but also spreads greatly by rhizomatous growth.

Reed canary grass is known primarily as an invader of wetlands, but at Pleasant Valley Conservancy we have found it in numerous upland sites. Surveys made at the time of flowering (when it is easiest to detect) have shown small patches of reed canary grass in most of our savannas, as well as in some of our oak woodlands.

This year, due to the initiative of Amanda and Marci, we instituted an all-out attack on reed canary grass, using clethodim (trade name Intensity), a grass-specific herbicide. Detailed surveys were made looking for the characteristic inflorescences. Note that the reed canary grass inflorescence resembles that of orchard grass, another nonnative invader, but the two grasses can generally be distinguished even at a distance. (We find orchard grass primarily along edges of prairies or lanes, whereas reed canary grass can invade almost anywhere.)

The photo to the left shows a typical small reed canary grass patch. The inflorescence can generally be seen at some distance. These upland patches are generally small, usually just a few leafy tillers and some flower stalks. Once seen, the worker bushwacks through the undergrowth to the site and sprays all the leaves in the patch. Generally a single spraying is enough to eradicate these upland patches (not true for the large clones generally found in wetlands).

A survey made this year in early June found over 100 small patches of reed canary grass in upland sites at Pleasant Valley Conservancy! All of these patches have been treated.

There are several grass-specific herbicides available for this work, including sethoxydim and clethodim. These agents are cyclohexanediones which act by inhibiting lipid biosynthesis in grasses. They have no effect on broad-leaved plants.

Details on the use of these grass-specific herbicides for reed canary grass and other undesirable grasses can be found in a concise paper published by Craig Annen in Plants out of Place, the newsletter of the Invasive Plants Association of Wisconsin.


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