Common Name: White Alder

General Information

Clethra barbinervis is a large, upright deciduous shrub or small tree that can grow around 1 - 9 metres tall with a spread of 3 - 4.5 metres[, ].
The plant is harvested from the wild for local use as a food. It is grown as an ornamental, valued especially for its fragrant flowers in late summer[].
Clethra barbinervis has a very wide distribution, large population, is not currently experiencing any major threats and no significant future threats have been identified. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2019)[].

Known Hazards

None known

Botanical References

, ,

Range

E. Asia - southern and eastern China, Korea, Japan.

Habitat

Wooded hills and mountains all over Japan[, ]. In sunny deciduous forests on mountains, more or less stony and dry places; at elevations from 1,000 - 1,500 metres[].

Properties

Conservation Status	Least Concern
Edibility Rating
Habit	Deciduous Shrub
Height	3.00 m
Pollinators	Bees, Butterflies
Cultivation Status	Wild

Cultivation Details

Clethra barbinervis is a moderately cold-hardy plant, tolerating occasional temperatures down to about -20°c according to some reports[, ], though some other reports say that it can fail if winter temperatures are consistently around its lower limits of tolerance[, ]. The new growth in spring is very susceptible to damage by late frosts[].
Requires a moist well-drained lime-free peaty soil[, , ] succeeding in a sunny position or partial shade[].
The flowers are fragrant, and are very attractive to butterflies and bees[, ].
Plants in this genus are notably resistant to honey fungus[].

Edible Uses

Leaves - cooked[, , , ]. Eaten with rice dishes[]. Commonly eaten in more remote areas of Japan[]. A famine food, the leaves are eaten with oil and salt[].

Medicinal

None known

Other Uses

None known

Propagation

Seed - sow early spring in a greenhouse[]. Only just cover the seed and keep the pot moist. Germination usually takes place within 1 - 3 months at 13°c[]. When large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for at least their first winter. Plant them out once they are more than 20cm tall in late spring or early summer after the last expected frosts.
Cuttings of half-ripe wood, 7 - 10cm with a heel, mid summer in a frame[, ]. Very easy[].
Root cuttings in December/January[].
Suckers in the dormant season[]. They can be planted out direct into their permanent positions if required.
Layering of current years growth in late autumn. Takes 18 months. Can also be done in early spring[].