Pruning Buddleja davidii is essential if you want to keep it looking its best. If you don’t prune your buddleia it can become tatty and overgrown, developing a twiggy tangle of bare stems, with the flowers appearing way above head height.
When to prune buddleia
Hard prune your buddleia in early spring. The most vigorous varieties will still grow to 3m tall and 2m across by summer, while the smaller forms, such as ‘Nanho Blue’, can be kept to less than 1.5m in height and spread. Alternatively, by pruning later in spring, you can ensure your buddleia flowers later in summer, to coincide with the emergence of the summer butterflies like the peacock and small tortoiseshell. Pruning as late as May can delay flowering until August, providing nectar when there’s little else available.
Bear in mind that Buddleja alternifolia and Buddleja globosa bloom on stems made in the previous season, so cutting back in spring would remove the flower buds. Neither should be hard pruned – instead, cut out a selection of the oldest branches in midsummer.
Where to buy buddleia online
How to prune buddleia
You will need:
- Secateurs
- Pruning saw
- Long-handled loppers
Step 1
First, trim back the top growth to around half its height, using secateurs. This makes it easier to see what you’re doing as you progress, and gives you better access to the base of the plant.
Step 2
Cut through the thick woody stems, around 30cm above the ground, using a pair of loppers or a pruning saw. Where possible, prune just above a bud or growing shoot. If you’d like the plant to grow taller than 3m (for example, if it’s at the back of a border), leave the stems up to 60cm long.
Step 3
Remove any dead stubs and branches using the pruning saw or loppers. Cut these back flush with the main trunk to minimise the chance of dieback. Also thin out any crossing branches to prevent rubbing, and remove any thin twiggy growth sprouting from the base. Don’t worry that you’re being too brutal, as buddleja is so vigorous that it will quickly re-grow.
Step 4
Aim to produce a short, strong framework of five to six main branches. It doesn’t matter if you can’t see many green shoots, as buddleja will produce new growth from underneath the bark. Fork lightly around the base to relieve any compaction you’ve caused by walking on the soil, and apply a mulch to the soil surface to retain moisture and suppress weeds.
Frequently asked questions
How do you prune an overgrown buddleia? An overgrown buddleia can be pruned in the same way. Remove top growth first, so you can see what you’re doing, and then use a pruning saw and loppers to prune back to a framework 30-60cm above ground level. It’s very hard to kill a buddleia so don’t worry about hard pruning such a large shrub. Do you deadhead buddleia? Yes, deadheading buddleia can prolong its flowering season, providing more garden interest as well as more nectar for pollinators.
