So how do you prune a Buddleja?

In most cases it is in March when you are in a bad mood! Summer flowering Buddlejas like the ubiquitous Buddleja davidii need hard pruning to encourage new flowering growth. Leave them unpruned and the excessive growth becomes wind damaged and vigour is lost resulting in poor flowering. Unpruned specimens of Buddleja davidii often grow in excess of 4 metres and become unruly, scrappy specimens. I often have to prune this plant using a pruning saw leaving a stump from which masses of new flowering growth will appear. 

What is important to remember is that Buddleja like many other genera of plants will compromise of many different species that have different patterns of flowering. Not all Buddlejas flower in midsummer; others flower in late spring and early summer on growth made in the previous flowering season. Hard pruning of these early flowering Buddlejas in March would remove all the flowering growth. The two most notable early flowering Buddlejas are Buddleja globosa (the orange ball tree) and the graceful Buddleja alternifolia. Both of these Buddlejas are best pruned after flowering taking out a selection of the older shoots. They certainly do not respond to the savagery meted out to  Buddleja davidii. 

Prune carefully after flowering- Buddleja globosa (above) and Buddleja alternifolia (below)

Buddleja davidii hard pruned in March. The plants are now over 2 metres (6 feet) in height and have forgiven my savagery!