Mares tail

It is a very difficult weed to get rid of, and I've heard people say "Best or only 100% answer is to move house. (Rather drastic)
I believe before using a strong weed killer on Mares Tail, you have to bruise the weed, breaking the surface as the waxy coating of the weed stops the weed kill being obsorbed into the plant. You have to treat all affected areas and it may require several applications. I hope this helps.

At the RHS garden at Harlow Carr near Harrogate they have been trying to rid a rockery of mare's tail for several years and it seems to have nearly gone. But that involved killing all the other flowers as well!

Sadly Chris this weed can send its roots down almost 2metres and similar plants date back to prehistoric times ! Almost impossible to uproot and impervious to chemical treatment as leaves so narrow do not absorb weedkiller.
Twin layers of weed suppress sheeting very successful but an awful lot of work - involves removing all plants double digging one sheet a metre down back filling soil then another sheet before re-inserting plants through slits.Sorry an easy solution to this doesnt exist or wed allbe doing it.