Buddleja davidii
Buddleja davidii
Common names: Summer lilac, Butterfly bush
At a glance
- Light
- Full sun
- Hardiness
- Hardy
- Pruning
- Feb–Mar
- Flowering
- Jul–Sep
Photo: --IKAl 15:22, 23 July 2007 (UTC) · CC BY-SA 2.5 · Source
This description was machine-translated.
Description
Buddleja davidii, commonly known as summer lilac or butterfly bush, is a semi‑evergreen shrub that produces long, pendant flower spikes from July to September. The spikes attract butterflies, bees, and bumblebees. The plant grows rapidly to 2 to 3 m tall and blooms on new growth each year. In Germany it is considered potentially invasive because its fine seeds disperse easily by wind and water, colonising gravel beds, railway embankments, and disturbed sites. To prevent self‑seeding, dead‑end flower spikes should be removed before seed set, and the plant should not be planted near protected natural areas. Cultivars such as ‘Black Knight’ and ‘Pink Delight’ offer additional colour variation.
Care instructions
Prune the shrub heavily each spring, ideally between the end of February and mid‑March (week 9 to 11), cutting to about one handbreadth above the old wood. This vigorous cutback promotes compact growth and abundant flowering, as the plant blooms only on new shoots. During the flowering season, regularly remove wilted spikes to extend bloom into autumn and prevent unwanted self‑seeding. The plant prefers full sun, a warm climate, and well‑drained soil. It tolerates drought once established. Water newly planted shrubs regularly during the first year; thereafter, watering is only necessary during prolonged dry periods.
The care notes were machine-translated from German.
Garden year
FloweringJul–Sep
Soil & site
Soil pH
Soil type
well-drained, lean, dry, lime-loving
The butterfly bush likes it free-draining and rather lean; it does not tolerate waterlogged soils at all. A sunny, sheltered spot with loose, limy soil suits it especially well. Loosen heavy, compacted soils best with sand or fine gravel before you plant.
Feeding
Light feeder
As an undemanding wild plant, the butterfly bush needs hardly any feeding. A trowel of mature compost around the root zone in early spring is entirely enough. Too many nutrients tend to lead to soft shoots and fewer flowers, so it is better to be sparing.
Pruning
Cut the butterfly bush back hard in late winter, ideally from the end of February to mid-March, shortly before new growth begins. Since it flowers only on this year's wood, it tolerates a radical cut-back to 30 to 50 cm very well and thanks you with abundant flowering in summer. You can also deadhead faded panicles during the season, which prolongs the flowering period.
Overwintering
The butterfly bush is hardy and usually survives winters in Germany without protection. In very harsh locations or with young plants, a mulch layer of leaves or brushwood over the root zone helps. Since it is cut back hard in spring anyway, a little frost damage to the shoots matters little.
Propagation
Methods
- Cuttings
- From seed
- Layering
The most reliable way to propagate the butterfly bush is from semi-ripe cuttings in late summer, which root in a few weeks. Sowing also works, but takes considerably longer to the first flowering. If you like it especially easy, layer a flexible shoot into the soil and wait until it forms its own roots there before separating it from the mother plant.
For your garden
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