Distylium racemosum Seeds | Isu Tree
LATIN NAME: Distylium racemosum
COMMON NAME: Isu Tree, Distylium, Winter Bloom
Plant Profile
The isu tree is an evergreen shrub or small tree of three to eight metres with leathery oval leaves, a dense rounded crown and small red flowers in short spikes in late winter. The flowers have no petals, only a tuft of red stamens, and they appear before the new growth.
It grows in the evergreen forest of southern Japan and of southern China, and it is one of the parents of the winter-flowering shrubs sold as witch hazel relatives. In Japan it is planted as a hedge and as a rootstock for Hamamelis, since it tolerates heat and wet ground that the witch hazels dislike.
Science & Biotechnology
The genus belongs to the witch hazel family, and its flowers are wind-pollinated rather than insect-pollinated: the red tuft is a set of stamens and stigmas exposed to the air, with no petals to attract a visitor. That is why the flowers are small and dull by comparison with a witch hazel.
The wood is exceptionally hard and dense, and in Japan it is used for the soles of planes, for mallet heads and for the handles of tools, where its resistance to wear matters more than its appearance. The tree also tolerates air pollution and clipping, which is why it survives in Japanese cities. The leaves are also browsed by deer in winter, which is one reason wild plants are often found on cliffs and in other places the animals cannot reach.
Uses & Benefits
The plant is used as a hedge and as a specimen in mild climates, where its evergreen leaves and its winter flowers are both useful. It is one of the few evergreens that will take a hard clip and regrow, which makes it suitable for a formal garden.
In Japan the timber goes into tool handles and into small implements, and the tree is grown as a rootstock for Hamamelis, on which the witch hazels flower more freely in a hot climate. In the West it is now sold in a range of garden forms, including dwarf and variegated selections.
Growing from Seed
Sow the seed in autumn, since it is short-lived, and keep the pot outdoors through winter. Germination is slow and uneven, and cuttings taken in late summer are a faster route to a plant of a named form.
Plant out in sun or part shade in moist, acid to neutral soil, and water through the first two summers. It tolerates clay and wet ground better than most evergreens, but not standing water. Clip hedges in late spring after flowering, since cutting in winter removes the flowers before they open. The tree also responds well to a hard cut in spring, and a hedge that has become bare at the base can be renovated over two seasons.
Our Take
An evergreen for wet ground and for clipping, with a small winter flower and a very hard wood. Not showy, but reliable where other evergreens sulk.
Related Reading
Readers interested in Isu Tree frequently explore these as well: