Omnia SanaThis tool aids identification but does not replace an expert. Never eat a wild plant or fungus on the strength of a single feature. When in doubt, throw it out.
Field Horsetail can be confused with 1 dangerous plant/fungus. Check every distinguishing feature before you trust an identification.
One of the most poisonous plants of wet grasslands. It contains the alkaloids palustrine and palustridiene together with high thiaminase activity; it is a well-known cause of livestock poisoning and should not be used in herbal teas. It closely resembles the medicinal field horsetail, with which it is confused and which it can adulterate.
Confusable part: Sterile green stems gathered and dried for horsetail tea; toxic marsh horsetail looks very similar and grows in the same damp ground.
Field horsetail (Equisetum arvense) is gathered for horsetail tea, but horsetails are notoriously hard to tell apart, and marsh horsetail (Equisetum palustre) - one of the most poisonous plants of wet grasslands - grows in the same damp habitat and looks very similar. Marsh horsetail contains the alkaloids palustrine and palustridiene plus high thiaminase (which destroys vitamin B1); it is a well-known livestock poison, and peer-reviewed work stresses that medicinal horsetail must be properly authenticated and differentiated from the more toxic marsh horsetail, which can adulterate herbal material. Because the species are so alike, unverified wild horsetail is a real hazard.
How to tell them apart
- Branch teeth: marsh horsetail (the toxic one) has 5-6 teeth on each branch sheath that lie flat (appressed) against the branch. Broad, spreading teeth in threes or fours indicate a non-toxic horsetail rather than marsh horsetail.
- Branches solid vs hollow: marsh horsetail has hollow branches, whereas field horsetail's branches are solid. A hollow first branch segment is a warning sign.
- First branch segment vs sheath: on marsh horsetail the lowest segment of each side branch is short - shorter than or about equal to the stem sheath it emerges from. A first branch segment clearly longer than the sheath indicates it is NOT marsh horsetail. Marsh horsetail also favours wet, marshy ground and fens.
Because horsetails are so alike and marsh horsetail is poisonous, only use wild horsetail if you can positively exclude marsh horsetail (Equisetum palustre): confirm branch sheaths have 3-4 spreading teeth (not 5-6 flat-lying ones), solid (not hollow) branches, and a first branch segment longer than the stem sheath. If you cannot confirm all of these - or the plant grows in wet, marshy ground - do not use it.
Educational identification aid compiled from the Omnia Sana plant database and cited botanical and toxicological sources. Not medical advice and not a substitute for expert identification.