This shrub is deciduous so it will lose all its leaves in autumn, then fresh new foliage appears again each spring. Position: full sun; Soil: moderately fertile, light, well-drained soil; Rate of growth: average; Flowering period: August and September; Hardiness: fully hardy The flowers of this handsome shrub are really useful for adding late colour to the border, and their rich purple-blue colouring looks wonderful against the foliage, which has a silvery reverse. Acting as a magnet for bees and butterflies, it’s a great addition to a wildlife-friendly garden, and once established, it will become drought-tolerant. Where temperatures fall below -15°C it’s best grown against a warm, south or west-facing wall; Garden care: In March prune all of the flowered stems back hard to the permanent framework. After pruning apply a generous 5-7cm (2-3in) mulch of well-rotted garden compost around the base of the plant.