Butterfly bush

Sun

Full sun; flowering is reduced and growth becomes loose in partial shade.

Water

Water regularly during establishment. Once established, water deeply during prolonged dry spells; avoid persistently wet roots.

Soil

Well-drained soil, including chalky, sandy or stony ground. Tolerates a wide pH range but struggles in waterlogged clay.

Height

6-12 ft (1.8-3.7 m)

Spread

4-8 ft (1.2-2.4 m)

Flowers

Summer to early autumn; the species usually has lilac-purple flowers with orange eyes. Cultivars include white, pink and darker purple forms.

Foliage

Opposite, narrow, pointed leaves, green above and pale grey-white beneath. Usually deciduous, though some leaves may remain through mild winters.

Growth

Fast; can produce several feet of new growth in one growing season.

Care needed

Medium

• Check local invasive-plant rules before buying or planting.
• Water through the first growing season whenever the root zone becomes dry.
• Apply a light layer of compost in spring; avoid heavy feeding, which encourages floppy growth.
• Mulch around the roots, keeping mulch clear of the stem bases.
• Remove spent flower spikes before seed capsules ripen, and pull out unwanted seedlings.

Pruning. In early spring, as buds begin to swell and severe frost risk eases, cut last year's shoots back to a low framework about 1-2 ft (0.3-0.6 m) tall. Remove dead wood and thin crowded stems; in cold climates, wait until new growth shows which stems survived.

Late winter

Check for winter damage, but leave major pruning until buds begin to swell.

Early spring

Prune hard to a low framework, removing dead or crowded stems.

Spring

Plant where permitted, water thoroughly, and apply compost and mulch.

Summer

Water young plants during dry weather and remove faded flower spikes before seed forms.

Early autumn

Remove remaining seed heads and pull seedlings from beds, paving and nearby disturbed ground.

Late autumn

Shorten exceptionally long stems if they rock the plant in wind; leave hard pruning until spring.

• Use at the back of a sunny mixed border, with lower perennials hiding its often bare base.
• Pair with ornamental grasses and coneflowers for an informal late-summer border.
• Place near a path or seating area to enjoy the fragrance and watch visiting butterflies.
• Use in a sunny gravel garden where local invasive-plant guidance permits it.

Garden styles it suits: Cottage garden, English country, Sensory garden, Dry gravel garden, Pollinator garden and Hot border.

Plant it with: Coneflower, Catmint, Russian sage, Yarrow, Stonecrop and Feather reed grass.

Wildlife: The nectar-rich flowers attract many adult butterflies, bees and other insects. It is not a significant caterpillar food plant in most places outside its native range, so include locally native larval host plants rather than relying on it alone.

• Root rot and winter losses in wet soil: improve drainage or move to a raised, freely draining site; do not keep the root zone saturated.
• Spider mites in hot, dry conditions: look for fine stippling and webbing, rinse leaf undersides, and use insecticidal soap if needed, following the label.
• Sparse flowering or floppy growth: provide full sun, avoid excessive nitrogen fertiliser, and prune in early spring.
• Unwanted seedlings: remove flower spikes before seeds mature and pull seedlings while small; replace the shrub where its spread cannot be managed.

Not known to be toxic to cats, dogs, horses or people; no part is recognised as a significant poisoning hazard. It is not an edible plant, and eating plant material may still cause stomach upset.

Where it spreads. Spreads aggressively by wind-borne seed in parts of the Pacific Northwest, including Washington, Oregon and coastal British Columbia, and is also listed as invasive in parts of the eastern United States. It readily colonises disturbed ground in the United Kingdom and is an environmental weed in parts of southeastern Australia, including New South Wales, Victoria and Tasmania.

• Alternate-leaved butterfly bush (Buddleja alternifolia)

  Has alternate rather than opposite leaves, with small lilac flower clusters strung along arching stems in late spring or early summer.

• Orange ball tree (Buddleja globosa)

  Bears round orange-yellow flower heads rather than long pointed spikes, usually in late spring or early summer.

• Common lilac (Syringa vulgaris)

  Has broad, usually heart-shaped leaves and flowers mainly in spring, unlike butterfly bush's narrow leaves and summer flowering.

Buddleja honours the English botanist Adam Buddle, davidii honours the French naturalist Armand David, and butterfly bush refers to the butterflies attracted to its flowers.

Propagation. Take softwood cuttings in late spring or early summer, or semi-ripe cuttings later in summer. Cuttings preserve cultivar characteristics; seedlings vary and should not be encouraged where the plant is invasive.

Accepted botanical name

Buddleja davidii

In the US and Canada

Introduced in Canada, Hawaii, the lower 48 states and Puerto Rico.

Native range

China North-Central, China South-Central, China Southeast and Tibet.

Measured

Soil pH 7 to 7.5. Average height 300 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.