Distylium racemosum aka Isu Tree

Distylium racemosum, or isu tree, belongs to the witch hazel family. This evergreen grows as a large shrub or small tree. Its native range covers parts of China, Korea, Japan and Taiwan. It grows in evergreen oak woods in its home range. Some Chinese sites lie at 3,280–4,265 feet [1,000–1,300 metres]. Its leaves stay on the plant through the year.

In gardens, it reaches about 8–15 feet [2.5–4.6 metres] tall. Sources give widths from 3–13 feet [0.9–4 metres]. Native trees can reach 60 feet [18.3 metres] in height. It grows slowly and forms a spreading crown with several stems. RHS gives five to ten years to reach mature size. The bark is brown, and young branches bear star-shaped hairs. Older branches turn dark brown and lose those hairs. The short, stiff branches carry leaves in an alternate pattern. Each leaf has a smooth edge and a wedge-shaped base. The glossy, tough leaves are dark green above and paler below. Their shapes range from narrow ovals to broader, rounded ovals.

Small flowers grow in upright racemes where leaves meet the stems. They have no petals, but red calyces and purple stamens add colour. RHS places flowering in late spring and early summer. Chicago Botanic Garden gives a broader season, from March through June. Woody capsules follow the flowers and appear in summer. Each brown capsule has two beaks and holds oval seeds. Brown, star-shaped hairs cover the fruit's surface. The capsules measure less than one inch across.

Grow this plant in partial shade, away from harsh, cold winds. It needs moist soil that drains well. Clay, loam and sand can all suit it. It also accepts acid, neutral and alkaline soil. RHS rates its UK hardiness as H4. US sources differ: Chicago lists zones 6–8, while NC State lists 7–10. Pruning is seldom needed, though NC State rates maintenance as medium. Raise plants from ripe seed or summer semi-ripe cuttings.

Use isu tree in borders, screens, hedges or woodland planting. It also suits foundation beds or a place as a specimen. Chicago lists it as attracting birds and butterflies. RHS and NC State report few pest or disease problems. The hard, dark wood serves for small objects and musical instruments. Wood ash also has a use in porcelain glazes. PFAF records no known food or medicinal uses. It lists no known hazards, but this does not prove safety.