Ceratostigma willmottianum aka Chinese Plumbago

Ceratostigma willmottianum is a small shrub that sheds its leaves each year. Gardeners call it Chinese plumbago or hardy plumbago. It belongs to the Plumbaginaceae family. Its native range runs from southeast Tibet into central China. Wild plants grow in warm valleys, beside woods, and in thickets. It forms a bushy plant with branches that arch outward. Underground rhizomes help it spread by rooting at their nodes.

Garden plants reach about 2–3.3 feet [0.6–1 metre] tall. NC State lists heights up to 4.3 feet [1.3 metres]. Spread reaches about 3–5 feet [0.9–1.5 metres]. Plants take five to ten years to reach full size. Growth proceeds at a moderate pace. The red-brown branches can be fragile. Fallen leaves may leave rings of scars on the stems. Green leaves sit alternately along each branch and have smooth edges. Their shapes range from narrow and pointed to diamond-like. Many measure about two inches long and have purple edges. They turn red or burgundy before falling in autumn.

Blue flowers open from late summer into early autumn. Sources describe their shade as pale or deep blue. Each flower measures up to about one inch across. Small groups form at shoot tips or beside the leaves. The blooms have a star-like shape with four or five petals. Bees, butterflies, and hummingbirds visit the flowers. The plant later forms seed capsules, which hold black seeds. NC State records fruit display in autumn.

Give this shrub full sun or some shade, not deep shade. It grows in sand, loam, clay, and chalk with good drainage. It accepts acid, neutral, and alkaline soils, including poor soils. Soil may stay moist or dry between waterings. Avoid wet ground, and water regularly during extreme heat. RHS rates it H4; NC State lists USDA zones 7b–9b. Spring pruning of surviving woody stems can improve bloom. Flowers grow best on new shoots. Semi-hardwood cuttings offer one way to raise more plants.

Use it in borders, containers, gravel gardens, or on slopes. Its flowers suit cutting, while red fall leaves extend seasonal interest. Care needs are low, and deer tend to leave it alone. Powdery mildew can occur; honey fungus is a rare risk. Sources report few pest problems. PFAF records no known food uses and mentions Bach flower remedies. That use does not establish medical benefit. ASPCA lists it as non-toxic to dogs, cats, and horses.