Buddleja can suffer from a few problems but these are easily remedied, mostly by pruning. Pruning should be rather straight forward but often plants are pruned too hard, too early (usually around late autumn and into winter), pruning this early can promote new shoots to grow through the early winter months, this is due to many Buddleja being semi-evergreen and happily continuing to grow through a mild winter. Once the frosts arrive in late winter (January/February) these young shoots are easily frosted and this can lead to a very late leafing up in spring or even loosing the plants altogether. The easy remedy is to prune established plants by a third in October/November to loosely shape the shrub then in late March/April you can prune the Buddleja down quite hard, even by another third if you wish and then the plant will grow away happily. This type of pruning will not affect flowering, a late spring/early summer light pruning will actually improve flowering and prolong flowers later into the season.
Another issue can be eelworm, this can look rather alarming as it presents itself as yellowish or brownish blotches through the leaf or as deformed shoots with blacken buds and twisted or deformed leaves, the best way to treat this is by cutting out affected branches or shoots and discard away from the garden, over time this will treat the problem.
A broader view of the Genus:
Buddleja’s are extremely useful shrubs for the garden, they offer wonderful flowers through the Summer, are easy to grow and very beneficial to insects. They are often viewed as large plants but there are many different species and varieties that offer all manner of flower types & colours as well as size. The flowers are covered with butterflies from mid to late Summer and the yellow varieties are particularly attractive to beneficial insects, this can offer a huge interest to the garden, it can be a real joy relaxing in the garden with a Buddleja in full flower.