Horsetails

7 July 2008

Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580   fax: 434.872.4578

~~~~~~~~~~~~~

For many folks the excitement of planting new varieties cannot be beat. It is fun to see what new hybrids will emerge each year as the new catalogs are published. But how would you like to have one of the oldest plants in your garden? Maybe something that has been around for 400 million years or more.

Horsetails (Genus Equisetum) have existed since the Devonian period 400 million years ago according to the fossil record. The Genus Equisetum is the sole survivor of a large group of seedless plants that hit their prime in the Carboniferous period some 300 million years ago. Based on genetic evidence they have been shown to arise from a common ancestor to ferns. Along with the club mosses and whisk ferns are referred to as fern allies, a diverse group of vascular plants that are not flowering plants or true ferns. There are 15 species of horsetails found around the world and four of these species can be found in Virginia.

Horsetails are rush-like plants with jointed stems. Their long creeping, underground rhizomes produce aerial stems at close intervals forming a colony. These stems are mostly hollow. Leaves are produced in whorls, reduced and fused into a sheath at the stem nodes. Looking at them close up you can see the surfaces of the stems are ridged longitudinally.

In the wild horsetails are mostly found colonizing unforested areas and wet areas such as ditches, edges of marshes, lakes, ponds, riverbanks, etc.

They are considered to be primitive plants for other reasons than their fossil records. They do not produce seed like the flowering plants we are familiar with but rather can reproduce with spores that are blown by the wind and travel through rain and dew. This they have in common with the ferns and club mosses that can be found in our woods. However, the majority of their reproduction is done vegetatively through rhizomes that stretch out as underground stems with roots below and aerial stems above.

Around the world horsetail species can range in size from 13 cm tall and 1 mm in diameter (E. scripoides) to 8 or more meters high and 4 cm in diameter (E. giganteum and E. myriochaetum).

Once used as a diuretic, horsetails have been formulated into different products and proclaim to aid with a variety of ailments. How much of it is research-based, I am not sure. Some species are said to be poisonous.

As a horticultural product horsetails have made it into the trade as water garden plant as they can tolerate up to 6 inches of standing water. While they prefer wet feet their rhizomes are also tolerant of simply moist soil and can be used to add to some interesting texture to a perennial garden as well assuming is does not get too dry. It is a hardy plant to zone 3 and like many perennials must be divided and cut back to keep it under control periodically as it can become invasive given the right circumstances. It can also be used as a houseplant if kept wet.

The horsetail pictured (Equisetum hyemale) is often called the scouring rush from its early use in scouring pots due to its high silica content. It is an evergreen species and its name hyemale comes from the Latin for winter.

~~~~~~~~~~~~~

For more information about this and other landscape topics contact your local Virginia Cooperative Extension office. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.