Shrub
How to grow buddleia (butterfly bush)
Buddleja davidii
Buddleia needs full sun and soil that drains; it is happier in poor, stony or chalky ground than in rich soil. Plant in March to May or September to October, allowing 2 m between plants. The job that makes the difference is pruning: cut every stem back hard to 30 to 60 cm in March, because it flowers on the current year's growth. Deadhead through August and September for a second flush and to stop it seeding around.
- Hardiness
- Fully hardy
- Position
- Full sun
- Soil
- Free-draining; tolerates poor soil
- Ideal pH
- 6.0 to 7.5
- Water
- Low
- Feeding
- Light feeder
Sowing and planting buddleia (butterfly bush)
WhenPlant Mar to May or Sep to Oct; prune hard Mar; flowers Jul to Sep
Starting off
Plant pot-grown stock Mar to May or Sep to Oct; it roots so readily that bare-root is seldom sold. Propagate by 10 cm softwood cuttings in Jun to Jul, rooting in 2 to 3 weeks at 18 to 20°C, or 20 cm hardwood cuttings in Nov in a sheltered trench. Seed germinates freely, which is why it must be deadheaded near railways and walls.
Spacing and planting
Unpruned it reaches 3 to 4 m by 3 m; cut back annually it holds at 1.5 to 2.5 m by 2 m, so allow 2 m between plants. Dig a hole twice the pot width and plant at pot depth. Dwarf 'Buzz' types manage in a 40 cm pot; standard B. davidii is not a container plant.
Varieties worth growing
- 'Black Knight'
- The darkest: long spikes of deep violet-purple in July and August on a tall, strong bush.
- 'Royal Red'
- Rich magenta-purple spikes among the longest of any buddleia; vigorous and reliable.
- 'White Profusion'
- Pure white with a yellow eye. Deadhead promptly, as white spikes show the brown as they fade.
- 'Lochinch'
- Silver-grey felted leaves and soft lavender, orange-eyed flowers into September; a rounder, more graceful shrub than the davidii cultivars.
- Buzz series
- Dwarf plants about 1.2 m high in magenta, violet, sky blue and ivory; bred for pots and small gardens, and pruned the same way.
Month by month
Timings are for central England. Allow two weeks later in the north and on cold, heavy soil.
- January
Nothing to do.
- February
Nothing to do. Hold off pruning until the worst frosts are over.
- March
Prune hard to 30 to 60 cm as the buds break. Plant. Feed only on very poor soil.
- April
Plant. Water new plants in dry spells.
- May
Plant. Pull unwanted seedlings from paving and walls.
- June
Softwood cuttings. Pick off mullein moth caterpillars.
- July
Flowering starts. Deadhead to the next pair of side shoots.
- August
Peak flower and peak butterflies. Keep deadheading.
- September
Last flowers. Remove every spent spike before the seed ripens. Plant.
- October
Plant.
- November
Shorten stems by a third in windy gardens. Hardwood cuttings.
- December
Nothing to do.
Feeding buddleia (butterfly bush)
A light feeder. In ordinary garden soil an established buddleia needs no fertiliser at all, and feeding gives long leafy stems with fewer flowers. Only poor, thin soils and pots get a little in March.
Low, vigorous and undemanding; over-feeding just gives leaf.
Feeding plan
Every year, ordinary soil
Nothing
No feed. The March prune is what drives new flowering growth.
Planting
5 g per litre of rootball dusted onto the roots so it touches them: 15 g for a 3 litre pot. Once only, and no fertiliser in the hole.
March after pruning, only on very thin or sandy soil where last year's growth was weak
50 g/m², half the label rate: about a handful (50 g) scattered round one bush and watered in. Once.
March, pots
2 g per litre of compost on the surface, the bottom of the label range, watered in: 60 g for a 40 cm pot (about 30 litres). Repeat once in June if the leaves are pale.
Signs to watch
Big soft leaves and long bare stems with sparse flowers
Nitrogen excess from feeding or rich soil
Stop feeding, no manure, prune hard in Mar
Yellowing older leaves on thin, chalky soil in Aug
Magnesium short in a fast-growing shrub
A single Epsom salts drench at 20 g per litre
Wilting and scorched leaf edges in Jul
Drought on a shallow soil
One deep soak of 20 litres rather than dail
Pests, diseases and problems
Young leaves at the shoot tips puckered and full of small ragged holes in May and June
Capsid bug feeding on the developing leaves
Tolerate it. The shoot grows on and flowers normally.
Leaves and flower buds eaten by fat white caterpillars marked with yellow and black, June and July
Mullein moth caterpillars, which feed on buddleia as well as verbascum
Pick them off by hand. Damage is over by late July and the bush recovers.
Leaves finely speckled pale and dull, then bronzed and dropping in a hot, dry summer
Red spider mite
Give one deep soak at the roots and hose the foliage on warm evenings. Plants against hot walls suffer most.
Shoot tips, or whole branches, dead in spring
Winter frost on soft late growth, or wind rock loosening the roots
Nothing to do but the March prune, which removes it. In windy gardens shorten stems by a third in November to stop the bush rocking.
Leaves crinkled, puckered and curled, with pale or yellow patches, as if diseased, most often in May
Usually aphids feeding under the leaves, reported on buddleia since 2023. It looks like a virus, but RHS samples tested free of virus
Tolerate it: the bush keeps its vigour and flowers normally. Turn a leaf over to confirm, and leave ladybirds and earwigs to work on the colonies. Do not dig the plant up.
Pruning
Pruning and care
Flowers on new wood, so cut every stem back hard to 30 to 60 cm from the ground in Mar, just as buds break; leaving it unpruned gives a leggy bush with small flowers. Deadhead spent panicles Aug to Sep to prompt a second flush and stop seeding. In windy gardens shorten the stems by a third in Nov to reduce rocking, then prune properly in Mar. No staking or winter protection needed.
Good to knowPrune hard in spring, it flowers on new wood. A butterfly magnet; deadhead to limit self-seeding.
Growing in pots
Only the dwarf kinds, such as the Buzz series, are worth growing in a pot; a standard buddleia is too big and too thirsty. Use a 40 cm pot of loam-based compost with some grit, in full sun. Water regularly in summer, as a pot-grown buddleia flags fast in heat, and deadhead often to keep it flowering into September. Prune in March as for plants in the ground, to about 20 to 30 cm, and top-dress with fresh compost at the same time.
Common questions
When should I cut back buddleia?
In March, once the hardest frosts are over and the buds are starting to shoot. Cut every stem of Buddleja davidii down to 30 to 60 cm from the ground. Buddleja alternifolia and Buddleja globosa are different: they flower on older wood and are pruned lightly straight after flowering.
Is buddleia invasive in the UK?
Buddleja davidii self-seeds heavily and has colonised railways, walls and waste ground, so it counts as an invasive non-native plant, though it is legal to grow in gardens. Deadhead before the seed ripens, especially near buildings and wild land, and pull stray seedlings while they are small.
Why is my buddleia not flowering well?
Usually because it was not pruned hard in spring, so the flowers are small and carried high on old leggy stems. Shade and over-rich or over-fed soil are the other causes. Prune to 30 to 60 cm each March, grow it in full sun and stop feeding.
Sources
Growing information on this page was checked against these references in November 2026. Feeding rates are Dr Forest label rates.