Distylium racemosum (Isunoki Tree)


Michael's Opinion

A strong addition to any landscape, with their strong roots, adaptability, and appealing colour that it retains all year round with little to no maintenance. I've personally grown fond of Distylium racemosum for its deep green foliage and the lovely, almost dark red coloured flowers in the early springtime. The anti-inflammatory and antioxidant medicinal properties this plant holds also piqued my interest, though these properties aren't surprising as this shrub comes from the witch hazel family, which is known to produce specimens with similar properties. They are also highly pest and drought resistant, which is of course ideal. However, I can see why it has not become too popular in the west yet, with it being fairly new to a scene in which buyers already have their favourites.

Botanical Information

FamilyHamamelidaceae
GenusDistylium
Speciesracemosum
CategoryWoody
TypeShrub (evergreen)
OriginThe genus Distylium is native to Southeast China, Hainan, Japan, Korea, Nansei-shoto, Taiwan, and Vietnam.

Details

USDA Hardiness Zone7a - 10b
USDA Hardiness Ref.
Canadian Hardiness Zone6a - 8b
Canada Hardiness Ref.
RHS Hardiness ZoneH4
RHS Hardiness Ref.
Temperature (°C)(-17.5) - 4.4
Temperature (°F)0 - 40
Height3 - 4.5 m
Spread0.9 - 2.4 m
GrowthSlow
Flowering PeriodFebruary, March, April

Description and Growing Information

General DescriptionSmall, pest free evergreen shrub that is easily adaptable with strong, lasting, coloured foliage.
ID CharacteristicSmall dense shrub with distinctive little maroon red flower clusters that have no petals surrounded by luscious dark green foliage. Found mostly in Asia.
ShapeUpright and dense, spread form.
LandscapeThey can be used for massing or hedging because of their strong root systems, resistance abilities, and ever present colouring.
PropagationPropagation is done through sexual or asexual methods; either through seed or cuttings. Seeds can be sown just before spring in cold frames and may require 2 - 3 months cold stratification. They are best sown as soon as possible following cold stratification. The germination period takes approximately 2 to 3 months at 15 C. Once large enough to transfer, they are best to be grown in a greenhouse till after their first winter. In the late spring to early summer they are then ready to plant in a permanent location. When achieved through cuttings, you can propagate them from semi ripe cuttings in the summertime for best results. Though mature, Distylium can be planted anytime of the year.
CultivationCan be lime tolerant, though a neutral to acid, moist, well-drained rich soil is ideal. Prefers sandy soil and grows under the thin canopy of other trees in partial shade or full sun. Grown best in mild areas and is slow growing, often does not exceed more than 2 metres.
PestsDistylium is impressive for its resistance towards pests and disease, as well as its resistance to deer and rabbit browsing. It has no known pests at this time.
HabitatFound primarily in evergreen oak forests, growing in the partial shade of the larger trees. These forests are at elevations of 1000 - 1300 metres.
Bark/Stem DescriptionThe stem attached to the foliage is green with downy small hairs, even more so on the stems attached to the flower buds. The older growth further down becomes a woodier light grey brown down to the base, with small lenticels visible and covering the bark.
Flower/Leaf Bud DescriptionThe flower buds are small, approximately 1.3 - 2.5 centimetres, oval in shape, with a light deep pink colour with soft, fine hairs. Flower buds are located on the axillary of the stems alongside the leaf buds. Leaf buds are light green and naked.
Leaf DescriptionThe leaves are entire, with a glossy dark green colour that can appear red from frost; able to hold said attractive colour all throughout the winter, even in full sun. Has cross-venulate venation and elliptic to ovate-elliptic leaves, 3.1 - 7.0 centimetres long by 1.3 - 3.8 centimetres wide. With alternate leaf arrangements, the foliage can become quite dense.
Flower DescriptionThe flowers are a maroon red, with a downy calyx and purple stamens. Having 5 parts yet no petals, the flower can be hermaphroditic -- meaning it has both stamens and pistils, and also has small upright racemes approximately 2.2 - 3.5 centimetres. Flowers bloom from February to April, sometimes starting as early as January.
Fruit DescriptionThe Distylium racemosum produces a two beaked woody capsule that appears star-shaped and brown with small downy hairs. Once the flowering period is over, it holds oval shaped seeds inside.
Colour DescriptionThe foliage of Distylium racemosum is a bright to dark deep green all year round. Some leaves, typically the younger ones, appear to have a light ring around the edges that's almost yellow or similarly coloured to the flowers produced, which are a maroon red colour that emerges from pink buds. The newer growth of the stem is a light green before fading to older grey brown coloured growth down to the base, which is much woodier. The bark is a medium brown. Spring frost can cause some yellowing to newer growth, whereas the falling leaves will turn reddish brown and once dead a light deep brown.
Texture DescriptionThe leaves have a rather leather-like feel to them, while the flowers and ends of the stems have a rather fine, soft velvet feeling. The bark is coarse yet smooth with ridges. The texture remains the same throughout the year.

Photographs