Buddleia davidii, the so-called butterfly bush, is too often seen to need a description and tooto waste a wall on, but many of the budclleias are half-hardy, or only just hardy, and are so much more uncommon than B. davidii that they are worth growing with the protection of a wall. B. fallowiana grows to about 2.7m (9 ft), has downy white shoots, and produces very fragrant lavender from July to September.
It can be cut right down by frost, but usually grows again from the base. Some of its hybrids, such as ‘Alba’, are hardier than the species, because they have been crossed with B. davklii. B. crispa has white down over all its, giving them a silvery appearance. It grows to 3m (loft), and produces from July to September. B. auriculata, 3m (loft), is evergreen in most winters, and is almost hardy on a warm wall in the south or west, but still needs protection even there in a hard winter. But it is worth taking some trouble with it, for it produces its very fragrant creamy flowers in September, and they go on to Christmas and beyond.
General care: Plant buddleias in March, the half-hardy ones against a west- or south-facing wall. They are happy in most soils, induding chalk, but like a sunny. back B. fallowiana and B. crispa in the spring.
Propagation: Take semi-hardwoodin August and strike in a 50-50 mixture of peat and sand.
Pests and diseases: Generally trouble-free.
Most familiar are the numerous varieties of Buddleia davidii, a normally rather tall, shuttlecock-shaped shrub with small, honey-scented flowers packed into conical spikes in late summer. Of this fine shrub there are lavender, purple, deep blue and white varieties. There are also other good species that are quite different in appearance, such as B. alternifolia, a big shrub with long, slender, archingwreathed in early summer with lavender-blue flowers, and B. globosa, open and rather gaunt in habit, with orange flowers in globose clusters which suggested its common name, orange ball tree. There is a hybrid between this and B. davidii, named B. weyeriana, but since the chief effect of the cross is to change the bright colour of the orange bes to a dirty mauve it is more of a curiosity than a decorative asset.
All buddleias thrive on chalk and limestone soils and grow well wherever the soil is well drained and the situation warm and sunny. All varieties of B. davidii can be cut back hard early each spring if desired, which somewhat reduces their size, though they can still reach 8 ft. in a season, and this improves the size of the flower spikes. B. alternifolia is best pruned in summer immediately after flowering, when the old flowering stems can be cut back to side shoots. With B. globosa it is usually sufficient to cut out weak and dead growth in early spring, but if bushes are too big they can be cut back, though with loss of flower that year.