plant that has been around since the dinosaurs. The best way to control horsetail is the same as for Japanese knotweed – keep knocking it back so that it gradually weakens.
Carex pendula is a self-seeding native that is quick to colonise. It has small roots for a plant that grows as big as it does, which makes it easy to pull or dig out. It is a problem for gardeners because, unlike most sedges, it grows well in dry conditions. Remove it before it spreads.
( Oxalis corniculata) is guaranteed to infuriate because it is tiny yet must be dug out or the fleshy tuberous roots will persist. It spreads like wildfire and is just as happy among the shoots of a potted perennial plant as it is in open soil. The last word should go to
which, down the years, has taken on the British landscape in style. The scourge of hill and dale, it is a defining menace that shows what can happen if persuasive weeds are allowed to take over.
Head gardener of Lowther Castle and Gardens Martin Ogle says that R. ponticum is the one serious weed that he has had to control. Years of grubbing out the stumps by hand and machine has proved effective.
This is the case for all persistent weeds: keep removing them and you will weaken them, and where possible intercept them before they can set seed. Good luck.