Common Horsetails

2016 May 28

These plants grow in great profusion in and beside the little stream that flows alongside of the road that we live on. I photographed them on May 11, 2016, while they were still showing their two distinct types of shoots. The first part to come up are the brown-and-black spore-bearing shoots, which are up to about 6 inches tall. These pop up practically overnight, and have no leaves or chlorophyll.


The enlarged head is for dispersing the spores, which are readily transported by wind and running water.


After the spore shoots have been up for a while, they are followed by the photosynthetic shoots. These are green, and look like little pine trees that can ultimately get to around a foot tall (note: they are not actually related to pine trees).

Once they get going, they make an almost continuous carpet of green all along the ditch sides and bottom.



These are Common Horsetails, Equisetum arvense, and boy are they common around here. They do particularly well in wet, organic-poor soil, like the ditches beside roads. They spread through an extensive network of underground rhizomes, which stores resources through the winter for their explosive growth in the early spring.

Horsetails are in a class by themselves – literally. They are the last surviving genus of plants in the class Equisetopsida, which were among the earliest land plants that developed roots and leaves. At one time, they were among the most plentiful land plants, and make up a lot of the volume of the coal seams that formed in the Carboniferous period. Other types of plants ultimately became more successful in most land environments, and now the 20 or so members of the Equisetum genus are all that is left of their entire class of plants.

Which isn’t to say that they are scarce. They’ve staked out a pretty distinct niche that they are well-suited for. The specific environment I found these in consists mainly of sand-filled and waterlogged areas that are too wet for most plants. In addition, the sand is mostly “stamp sand”, crushed basalt left over from when this was a copper-mining district. The county road commission spreads this sand on the roads in the winter to give traction on ice, and then when the spring comes most of it ends up pushed into the ditches. The thing is, the stamp sand contains a small amount of copper, making it mildly toxic to most plants. But, the horsetails evidently have better metal resistance than their competitors, and so they can tolerate it. So, in this particular environment there is very little competition, and what competition there is they can brush aside without too much difficulty.

One of their limitations is that they do spread by spores rather than by seeds. Spores are not the same as seeds, they are armored haploid cells that do not contain any nutritional reserves and can only successfully sprout if they land in a spot with ideal growing conditions. Once a spore successfully sprouts, it does not form the parent plant. Instead, it makes a sexual form that has to breed with the offspring of other spores to produce a zygote that eventually grows into the spore-generating form of the plant. Since spore germination is a low-probability event, there is a lot of incentive for the horsetails to aggressively spread vegetatively through their rhizomes as much as possible. So, the individual patches of horsetails along our road probably each came from single zygotes, so there might never have been more than maybe a dozen or so initial plants.

4 Responses
  1. May 28, 2016

    An interesting merger of your new study of plants with your old one of insects would be to include a photo of an insect on the plant with a discussion of their relationship, possibly through a link to a previous post.

  2. Carole permalink
    May 28, 2016

    Very interesting, but sad. Roadsides are usually such diverse habitats of plants and insects.

  3. May 31, 2016

    KT: Yes, that is a good plan. I do have to kind of make do with what nature hands me, though – I have yet to see any insects actually eating the horsetails. But, once I get to things like aspens, which it seems like just about everything eats, then it is a whole ‘nother ball game.

    Carole: The horsetails mainly just grow right up at the edge of the road. Once you get a few feet away, away from the stamp sand and up where it is drier, the plant diversity spikes up pretty abruptly.

  4. June 20, 2016

    I stumbled across your website trying to identify the day-time firefly that I spotted a few of flying in my yard less than an hour ago. I live in the northern corner of NY near the Adirondacks, and have horsetail all over my yard. It seems to spread like wild fire here. Last year we had some sprouting up, this year we have bushy patches of it growing all along our garden in sand. Nothing I have found will rid them from my yard. On my previous research on this plant, it is pretty hardy. I can’t imagine much actually getting rid of horsetail. I read that it was one of the first organism to reestablish in the blast zone of Mount Saint Helens.

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