Horsetail (Equisetum), Clevancy

Image: © Vieve Forward Taken: 31 Jul 2016

The Horsetail family (Equisetaceae) is a remarkable group of plants, now restricted to about 25 species, found in most parts of the world. They were formerly of greater importance: in Carboniferous times they were at their height and formed an important part of the vegetation. Many fossils of related species are known, with very diverse forms, and many grew into trees. These included Calamites and Sphenophylls (a completely extinct group) which were in many respects (i.e. cone and leaf structure) more complex and highly organized than their modest descendants. The present-day forms all have underground stems, and erect tubular jointed stems which bear sheaths of scale-leaves. These leaves are the only ones the plant possesses, and they are very much reduced; the whorled branches (when present) grow out through the base of the sheath. The stem is much coated with silica; in fact there is often enough silica to leave a skeleton after the removal of the vegetable matter. The cones produce spores, the outer coats of which split into 4 narrow strips forming 'elaters', which by their hygroscopic movement disperse the spores. The latter germinate very soon after dispersal, forming prothalli of 2 kinds, one bearing male and the other female organs. Fertilization occurs, and the new horsetails develop. (Information from Prime & Deacock's Shorter British Flora, 1963). Prime & Deacock list five species in Britain. As a gardener, I can vouch for the fact that horsetails are practically impossible to eradicate from a garden: the roots go down 3 feet or more, and will always regenerate, no matter what.

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