WHEN AND HOW TO PRUNE BACK BUDDLEJA

When and how to prune back Buddleja

Understandably, many gardeners will see Buddleja species and cultivars as little more than weeds. However despite their apparent ubiquity, their flowers are a valuable a nectar source for many species of butterfly (hence the common name of butterfly bush), and twenty species and cultivars have been awarded the prestigious Award of Garden Merit from the Royal Horticultural Society.

When and how to prune back Buddleja
Buddleja are most notable for their blooms, so to get the most out of your buddleja you need to prune them appropriately and at the right time of year.

Surprisingly, for the majority of species no regular pruning is required. That being said, Buddleja davidii species and cultivars (with an unchecked height and spread of over 3 metres) can be kept to a manageable size by pruning in March. Cut all of the previous years growth back to within 5-10 cm of the old wood. This will cause the plant to produce strong, erect stems and large flower clusters.

When and how to prune back Buddleja
Species such as Buddleja globosa and Buddleja colvilei flower on the previous year’s growth, should be lightly pruned after flowering by removing the faded clusters with approximately 5 cm of stem. Buddleja alternifolia can be kept neat and bushy by removing two-thirds of all stems after flowering.

After pruning always mulch the base of your Buddleja with well-rotted farm manure or garden compost. To help the following season's blooms you can also provide a high potash, slow or controlled release fertiliser.