To be or knot to be

IF you like fuss-free tough plants that flower for months, persicaria (knotweed and bistort) should be on your shopping list. Producing airy tapers of crimson, raspberry, pastel pink or ivory flowers, they add colour and informal style to borders and provide bees with nectar. These stalwart perennials can bloom from July into October, and sometimes November, and provide attractive foliage that can take on fiery tints in the autumn.

However, it’s crucial to select the right type of persicaria! Upon reading the word knotweed, most gardeners will reel, thinking of the infamous Japanese knotweed (), which, indeed, used to be grouped within the same genus before being recategorised. Some species of persicaria, including and , can spread at an alarming rate