Generally butterfly bushes are tolerant of any soils, particularly in full sun. Evergreen or deciduous shrubs, with opposite leaves (except for the contrary B. alternifolia). 4-petalled flowers, in small rounded heads, or long spikes, often sweetly scented. Many will flower in late summer, coinciding with the arrival of migratory butterflies like the red admiral. Perfect for them for a nectar hit and for the buddlejas to be pollinated. B. davidii from China has naturalised on waste ground, railway verges and even buildings. Most (but check the species) can be left unpruned over winter, but then cut back to a framework of your choice during spring.