gala - are you confusing with horsetails? Mare's Tails are an aquatic species.
You probably have Equisetum arvense in your garden; Mare's tailis Hippuris vulgaris.
Hi,frugalfred,I thought mare's tail and horsetail were the same plant.Never stop learning,eh? Really difficult to get rid of as you will know, galasalmon
Yes, gala - the horsetail was widely planted in the early days of railway development to stabilise the sides of embankments, as it has a very deep root system. This deep root is the reason it is so difficult to get rid of from the garden.