Yep its horestail / marestail its a real bugger This is from the internet
Horse or Mares Tail
Horse or Mares Tail, Equisetum Arvense is, in my opinion, public enemy number one. It looks like it belongs in Jurassic Park and, unchecked, spreads like wildfire.
In spring, brown green shoots appear with small cones at the tips that produce spores. (Arghh – millions of ‘em) and it grows away from creeping thin brown roots that you can hardly see as they are soil coloured. Digging out these roots is not feasible – they go down into the soil for up to 1.5 metres – yes, 5 feet.
Later the ‘leaves’ or tails appear. These will die off as autumn turns to winter and the roots sit there waiting for spring. The leaves have a waxy coat, which makes the plant highly resistant to weedkillers.
Crushing the leaves to break up the coating helps weedkiller to penetrate and become absorbed but in large areas it is not so easy to crush all the leaves . However, glyphosate weed killer will have an effect and eventually kill the plant. You will probably need 5 or more applications. Knock it back, it re-grows and you repeat.
I don’t think you can clear this in less than one season.
Ammonium Sulphamate seems to be a far more effective weed killer. It can kill it in one application but may well need two. It used to be available as Amicide but now you need to look for a brushwood killer that incorporates it like Rootout or Deep Root. Just check the packet for ammonium sulphamate.
I’d recommend NOT digging where there is horsetail until it is dead for sure. Otherwise it just starts springing up from the root cuttings. Drying or drowning the roots prior to composting is a must.
