Viburnum opulus var. sargentii ("Kanboku")

Japanese name: カンボク （肝木）
Scientific name: Viburnum opulus var. sargentii

[Overview]
A deciduous small tree about 6 m tall, growing in slightly moist places in forests and at forest edges in the mountains.
Young branches are green, sometimes tinged with dark red, and hairless.
Leaves are opposite, broadly ovate, 4–12 cm in both length and width, and 3-lobed to about the middle.
On the upper surface three veins stand out, the veins are sunken and wrinkled, and the margin has coarse teeth.
The upper surface is almost hairless, and the underside has fine hairs.
The petiole is long, 1.5–5 cm, often tinged with dark red, with 2–4 disk-shaped glands near the tip and stipules near the base.
The leaves are rarely simple and unlobed.
At the branch tips, flat corymbs 6–12 cm across are produced, and the base of the inflorescence usually has 2 pairs of leaves.
The flowers are white, about 0.4 cm across, and scented.
Around the inflorescence are white ornamental flowers 2–3.5 cm across, and the corolla is 5-lobed.
The fruit is spherical, 0.6–0.9 cm long, and ripens red, but it is not edible.

[Uses]
The branches, leaves, and bark are used medicinally.

[Cultivation]
Propagate from seed or cuttings.
For seed, collect ripe fruit, wash off the pulp thoroughly, and then sow.
It grows well regardless of soil type as long as the site is sunny or partially shaded, well drained, and rich in humus.
Rainfall is sufficient unless summer brings a long spell of sunny weather and the soil becomes severely dry.
Apply fertilizer in winter, and also apply a slow-release chemical fertilizer with equal amounts of the three components after flowering as a thank-you fertilizer.
No pruning is done and the natural shape is enjoyed, but to keep it compact, cut just above a bud as soon as possible after flowering.
Poor ventilation makes powdery mildew and scale insects likely to occur, so care is needed.

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