Archive for April 13th, 2010

Scouring Rush

The Horsetail genus Equisetum comprises 15 species, which can be divided into two subgenera. The subgenus Equisetum, the bushy horsetails, have needle-like whorls along deciduous stems that die back to the rhizome each autumn, along with separate stems that produce spores. The subgenus Hippochaete, the scouring rushes, are typically bamboo-like, jointed, unbranched, evergreen stems. They produce spores in terminal ‘cones’ that appear on the tips of the reeds in spring or summer. Common Scouring Rush (Equisetum hyemale) is indeed very common around here. Field Horsetails can cope with dry habitats such as fields and roadsides, but Common Scouring Rush retains its ancestor’s preference for damp ground. It grows along the river, and in wet ditches along the roadside beside swampy areas.

While spores released from their stem-top spore cones may produce new colonies if they land on fertile ground, the rushes mainly reproduce by cloning. They have creeping rhizomes, which may extend in a network for hundreds of feet. The name scouring rush comes from the rough surface of the stems. The roughness is the result of the plant’s uptake of silica in solution. The silica becomes crystallized in the plant tissues. Silicate levels may be as high as 15 % by weight. A plant that has been around for 65 million years knows what it is doing. The gritty silica makes the plants less palatable to herbivores. However, scouring reeds have long been used as a handy pot scourer by outdoors enthusiasts.

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