Buddleja alternifolia aka Alternate Leaf Butterfly Bush

Buddleja alternifolia has two common names: fountain and alternate-leaved butterfly bush. This shrub sheds its leaves. It belongs to the figwort family, Scrophulariaceae. It comes from Tibet and northern and east-central China. It grows in thickets by rivers and dry river beds. Gardeners grow it for its drooping form and sweet-scented flowers.

It forms a large shrub with several woody stems. Garden plants reach 8–15 feet (2.4–4.6 metres) tall. They spread 10–18 feet (3–5.5 metres) wide. RHS lists a smaller range for both height and spread. This is 8–13 feet (2.5–4 metres). Tree forms can sometimes reach 20 feet (6.1 metres). Long, thin branches curve out, then hang toward the ground. Train one trunk to form a small weeping tree. Smooth bark ranges from dark brown to pale green. Narrow leaves have a lance shape, like a spear tip. They grow one at a time, on alternate sides. Their tops range from green to silvery green. Thick grey-white hairs cover the leaves beneath. Leaves may turn yellow before they fall.

Small lilac-purple flowers open from May to June. Each tube-shaped bloom has a mild, sweet scent. Tight groups of flowers line shoots from the year before. These groups can look like one long flower spray. Bees, butterflies, and moths visit, as do other pollinators. The plant also feeds caterpillars, and birds eat its seeds. The fruit is a smooth, oval capsule that holds seeds. These narrow, oblong seeds have wings.

Full sun gives the best show of flowers. It grows in part shade but blooms less in deeper shade. It accepts clay, loam, sand, and chalk soils. Acid, neutral, and alkaline soils can all suit it. It prefers loose soil rich in organic matter. Water must drain well; the roots cannot stand wet ground. Once plants take root, they cope with heat and drought. They also cope with poor soil. A fair amount of moisture helps garden plants grow. Sources list USDA zones 5–9 and UK hardiness H6. Prune a little after bloom to keep next year's flowers. Do not cut it down in late winter. Growers can raise new plants from semi-hardwood cuttings.

Use it in shrub borders, beds by buildings, or cottage gardens. Its size suits screens or planting as a single showpiece. Its flowers and value to wildlife suit butterfly gardens. It rarely has serious pest or disease problems. Aphids, capsid bugs, and caterpillars may attack it. So may earwigs and weevils. Spider mites and leaf or bud eelworms are also possible. Honey fungus, fungal leaf spots, and viruses can occur.