Horsetails and Scouring Rushes
Equisetum spp

Hidden among the more familiar plants in our fields and woods are a group of relict species, survivors from an earlier evolutionary time, the horsetails and scouring rushes.

You can link here to find out more about the geological time scale.

From about 380 to 280 million years ago, the mid Devonian through the Mississippian/Pennsylvanian, plants of this group were an important part of the landscape and were an important part of the base of the food pyramid for terrestrial ecosystems. The horsetails and scouring rushes were among the first to solve the problem that had plagued earlier terrestrial plants such as mosses and liverworts - how to move water within the plant. Their solution was the evolutionary development of vascular canals, tubes within the plant that transport water from the root-like rhizomes up to the stems and leaves. This was a giant step for plant-kind and a vast improvement over the earlier method of capillary action.

The vascular canals allowed the plants to grow upwards toward the sun instead of merely being creeping mats. They towered up to 60 feet into the air and had massive trunks. These trunks subsequently formed much of the petrified wood we find in our western deserts and, as dead trunks accumulated on swamp floors, they formed great coal deposits. So numerous were they that the accumulation of just their powder-like reproductive spores formed the beds of anthracite coal, the hardest and best burning coal.

Other types of plants subsequently built on the success of the vascular canals and ended up displacing these pioneers. But these were among the first members of the modern group known as the vascular plants, a group which now includes not only the ferns and conifers, but also the modern flowering plants.

The modern survivors, comprising a single genus Equisetum in the group Equisetophyta, are small and are usually not the dominant species in a community. All are recognizable by the jointed structure of the stems, which gives them one of their common names: jointweed. Not very many species of Equisetum remain, probably only 15 different species in the whole world. Therefore it's been somewhat surprising to learn that 10 of those 15 may be found in the Boquet watershed. I have verified the presence of 8; the other two are probably there but I haven't had a chance to go to the habitats where they are likely to be found. How a small area like our watershed can hold so many of these survivors is an unanswered question.

The modern group Equisetum is divided into two subgroups: those where the stem does not have branches (usually referred to as scouring rushes) and those where the stem does have branches (usually referred to as horsetails).

Equisetum x ferrissi

There are four scouring rushes in our area: Equisetum scirpoides (dwarf scouring rush), E. variegatum (variegated scouring rush), E. hyemale (rough scouring rush), and E. x ferrissi (Ferriss' scouring rush). The last of these is our most common scouring rush and forms dense beds in damp areas, especially in disturbed areas along roads. The dark green stalks are present year round and are especially noticeable in the early spring when they look like the bristles of some giant industrial brush. The "x" in name E. x ferrissi indicates that it is a hybrid species. At some point in the past, two different species of scouring rush cross bred and produced the hybrid E. x ferrissi. The hybrid grows very well and even seems to exhibit what geneticists call "hybrid vigor," but, like the mule, it is sexually sterile. However this sterility is no drawback for this scouring rush; by reproducing vegetatively it has spread across much of North America. Fragments of roots transported by man or nature take hold and start new clumps. Then the clumps grow by spreading along underground root-like structures called rhizomes. All of the Ferriss' scouring rushes we have today appear to be clones from the original hybrid.

Equisetum arvense

Of the branched horsetails, the most common in our area is E. arvense (field horsetail). As the name implies it is found in fields and other areas and is a good colonizer of disturbed areas. The coarse green vegetative stems of the plant are familiar to most gardeners and anyone who walks the land. Early in the spring, before the green stems come up, this species produces a specialized straw-colored unbranched stem that bears the spore forming organ, the strobilus. Another horsetail, E. pratense (meadow horsetail), a threatened species in New York State found in our area, also has this type of spore bearing stem, but the other scouring rushes and horsetails bear the spore-forming strobilus on the ends of the green vegetative stems. The other two horsetails known to be in our area are E. sylvaticum (woodland horsetail) and E. palustre (marsh horsetail).

The stems and branches of all of the Equisetum species are coated with silica granules. This accounts for the common name "scouring rush" as it made them useful in earlier times for scouring pots and pans (although it's a little tough on modern teflon coatings). The silica granules also make Equisetum very irritating to the stomach of cows that feed on them, so farmers are not pleased to find them in their fields.

All species, like the scouring rushes and horsetails, have their histories and each tells a story. This is one of the reasons biodiversity is so fascinating.
 

Plants Boquet River