A tale of the strange horsetail in the wood

Posted on 21st November 2016

Great Britain has one of the most studied floras in the world but there is still more to find…


Whilst preparing for the walks in Whitecliff Wood this summer with the group from the Cleveland Ironstone Mining Museum I noticed something odd about what I’d always taken to be a large patch of Giant Horsetail but I couldn’t work out why at the time. As I was in a hurry, I took a few photographs and resolved to check my reference books when I got home.


My photographs showed a plant with secondary branching and all my reference books said Giant horsetail only has primary branching.

So I looked at hybrids – did you know Horsetails hybridize? No, me neither. Anyway, there was a possible hybrid of Giant Horsetail crossed with Wood Horsetail (which does have secondary branching). I had a look on the internet to see what it looked like. It is very rare – found only in two places in the UK.


I went back to the wood, carefully collected a sample and pressed it. Once fully dried, I posted it off to the Natural History Museum for the attention of the national referee for Horsetails (through the Botanical Society of Britain and Ireland (BSBI)).


He replied saying that it was Giant Horsetail and he had just re-written the reference book from ‘never has secondary branches’ to ‘rarely’ . The sample I had sent in was only the third example he had seen in recent times and he had found no examples in the Natural History Museum herbarium, so it is a very rare mutation. At least we think it’s rare; the BSBI expert wrote to me “…it may just be that I never looked before. I always do now.”

…which just goes to show what can still be found if you keep your eyes peeled.