Bowles' Mauve wallflower

 One of the best plants for butterflies and Bumblebees, this lovely perennial wallflower will flower from early spring right through the year and make a mound of bluish foliage with deep purple flowers that is just as good in a patio tub as in a small rock garden. Ideal for small urban gardens or a front garden. It likes well-drained conditions. (Although called 'perennial' it does tend to become leggy and die out after about 3 or 4 years, so it's good to take cuttings if you can)