Jumping horses

This is the ‘Grass bed,’ so called because of the row of Stipa tenuissima running along the back.
As you can see, at the moment it’s full of forget-me-knots, Erysimum ‘Ivory Giant’ and tulips either in flower, or still to come.  Last year’s Narcissi ‘Sinopel‘ seem to have gone blind this year which is a shame, but bearing in mind the bed faces north, they did all insist on looking the other way, rather than towards the garden, which struck me as rather rude, particularly bearing in mind how expensive they were.
What you can’t see, is that later in the summer this bed is plagued with mare’s tail (Equisetum arvense), and I spend quite a lot of time trying to keep on top of it with varying levels of determination depending on what else is going on.
Having had a problem with it years ago on my London allotment, I’m aware that the roots go deep, but a little investigation has suggested they go down 2 metres.  What I can’t quite fathom, even bearing this in mind, is whether there is a relationship between the mare’s tail in the grass bed, and that growing more like 3 metres below at the road side:
However new information has recently come to light in the form of the quarterly “Kew” magazine.  Apparently the physicist, Philippe Marmottant of Joseph Fourier University in Grenoble, has filmed the movement of mare’s tail spores with a high-speed camera and discovered that the way they move is humidity dependent.  
At high humidity the spores appear spherical, but as the air dries they change shape – at 75% humidity four ribbon like ‘arms’ unfurl, reaching their full extent when humidity drops to 50%.  Because this movement is related to the different structure of the inner and outer layers of the ‘arms’, the process can be repeated again and again, resulting in the spores ‘walking’ – albeit very slooooowly.  Conversely, when fully hydrated spores are exposed to sudden drying, they ‘leap’ from the ground, reaching a height as much as a…….centimetre. Now a centimetre may not sound much, but it takes the spores out of the still air at ground level and into moving air that can transport them into new areas to colonise.
So the question is, did my mare’s tail come from creeping rhizomes that haven’t read the RHS’s 2 metres fact, or from ‘jumping’ spores, caught in an updraft of a passing car and deposited on my bed?  I’m really not sure, I just wish it was neither.

1 thought on “Jumping horses

  1. Chloris

    I had the dreaded mares’ tails in my last garden. They are virtually impossible to get rid of. I have read that the roots have been seen in coal mines. Chop the flowers off quickly before those spores can jump anywhere.


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