Red Valerian, 3 plants in 7 cm square pots
Red Valerian is typically found growing on chalk cliffs and other places hostile to potential competitors. You could try to recreate its natural environment by adding some soil to a crack in a wall and planting it there. So long as there is not too much competition, it will do well in ordinary garden soil, although if its too fertile it may put on lots of leafy growth at the expense of flowers.
Value to Wildlife
Not introduced into Britain until the 16th century, it does not appear to have evolved any special relationship with any species of native lepidoptera and tends only to be eaten by a small number of generalists including the Large Ranunculus Moth, Polymixis flavicincta (wingspan 40-50mm) which eats a wide range of plants including Ragwort, Dandelion and Rosebay Willowherb, and the night flying Angle Shades Moth, Phlogophora meticulosa, (wingspan 45-52mm) which consumes an extremely wide range of herbaceous plants and trees.
You are purchasing three well-rooted plants in 7 cm square pots.