These shrubs are a favorite for attracting butterflies, as their common name suggests. Most butterfly bush varieties have gray-green foliage and clusters of showy, fragrant flowers in shades of pink, purple, blue, yellow, or white from summer to autumn.
- Common name: Butterfly bush
- Botanical name: Buddleja davidii
- Zones: 6 to 9
- Size: To 15 feet tall and wide
- From: areas of Asia
- Family: Loganiaceae (logania family)
- Sun: Full sun or partial shade. Partial shade is best in especially hot-summer areas.
- Soil: Moist, well-drained soil is best. The plants are adaptable to different soil types.
- Moisture: Water during times of drought to keep the plants looking healthy and to encourage plenty of blooms.
- Zones: 6 to 9, but because these shrubs bloom on new wood, gardeners in northern zones (Zones 4 and 5) can treat them as an herbaceous perennial that dies back to the ground each year. Gardeners in northern zones can try growing these shrubs in large pots and overwinter the pots in an unheated garage or storage shed for winter.
- Mulch: Mulch around the base of the shrub to conserve soil moisture and block weeds. Keep the mulch layer about 2 inches deep and 4 inches away from the shrub's stems.
- Pruning: Butterfly bush blooms on new wood, so prune it in winter or early spring before it begins to grow. It can be cut back severely-almost to the ground each season-to keep it compact.
- Fertilizer: In average soil, it doesn't require fertilizer. If fertilizing, use a balanced product such as a 10-10-10 or a timed-release fertilizer in spring.
- Seed: Seeds germinate best at temperatures between 65 and 75F. One note: Seeds from hybrid plants (named cultivars such as ‘Harlequin') may not produce plants that look like their parents.
- Cuttings: Take cuttings in mid- or late summer. Cuttings tend to root quickly and easily.
- Aphids: These small insects often appear in large numbers on new growth. Spray them daily with water; they will not attack a plant after being knocked off. Use an insecticidal soap or neem-oil-based spray if infestations are severe.
- Leaf spot: In summer or autumn, the leaves develop yellow or dark spots. Each spot often has concentric rings around it, forming something of a bull's-eye pattern.
- Weevils: If your plants grow, but don't thrive, the problem may be weevils. These insects often go unnoticed because the larvae feed on roots. Adults, which look like beetles, may consume leaves or flowers. To deter weevils, attract beneficial insects or use sticky traps around the base of the plant.
There are many cultivars available. Here are a few:
- Buddleja davidii ‘Attraction': A compact selection to 6 feet with purple-red blooms.
- Buddleja davidii ‘Black Knight': A selection with especially dark purple blooms.
- Buddleja davidii ‘Dartmoor': A compact selection with lilac flowers. To 6 feet.
- Buddleja davidii ‘Harlequin': A selection with magenta flowers and variegated foliage.
- Buddleja davidii ‘Nanho Blue': A selection with light blue flowers on dwarf, 5-foot plants.
- Buddleja davidii ‘Pink Delight': A selection with pink flowers.
- Buddleja davidii ‘White Bouquet': A selection with white flowers.