Great horsetail
Equisetum telmateia
Family · Equisetaceae · Poisonous
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This plant, or one that resembles it, is dangerous. Identifying is not authorising: no app has the authority to tell you that you may eat or touch a plant.
Emergency
Europe's largest horsetail, forming miniature forests of white stems with whorls of fine green branches, on banks where water seeps. It is a plant with three hundred million years of design behind it.
Streams and ditches · Oak woods · Roadsides and waste ground
Also known asgiant horsetail
How to tell it
A sterile stem of ivory white or very pale colour, hollow and grooved, with whorls of fine horizontal green branches at each node, giving the look of a small pine. In winter, brown branchless fertile stems come first, ending in a spore cone. It never flowers.
What it is confused with
Branched horsetail
Equisetum ramosissimum
Common horsetail is green, slimmer and branches irregularly; the great one has a thick white main stem and branches in perfect regular whorls. Both contain thiaminase.
What it is for
Much used in traditional infusions for the kidneys and still sold today. It is not a harmless plant: it contains thiaminase, which destroys vitamin B1, and prolonged use has caused serious deficiency in animals with described human cases. The silica in the stem served to polish wood and pewter, and there it is unmatched.
With documented traditional uses. Not a therapeutic indication and not a dose.
Where it occurs
Each square is an area with recorded observations of this plant. The lighter background is the set of areas where any of the entries has been observed, and serves as a reference. Note what this is not: it is not where the plant lives, it is where people record it, so trails and towns always look fuller than the mountains. Data from GBIF.
Sources
Community
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