Japanese Alder
Alnus japonica
Family: Betulaceae
What it is like
Alnus japonica is a deciduous Tree growing to 22 m (72ft 2in) at a fast rate. See above for USDA hardiness. It is hardy to UK zone 4. It is in flower from February to March. The species is monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and is pollinated by Wind. It can fix Nitrogen. Suitable for: medium (loamy) and heavy (clay) soils and can grow in heavy clay and nutritionally poor soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers dry moist or wet soil. The plant can tolerates strong winds but not maritime exposure.
Height (m): 22
Where it is found
Wet lowlands all over Japan.
E. Asia - China, Japan.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 0
Medicine
Rating: 1
Various species of alder, including this species, seem to contain antitumour compounds.
Cancer: Used in the treatment of cancer.
Other
Rating: 2
A dye is obtained from the bark. No more details are given. Wood - close grained. Used for turnery, charcoal.
Charcoal: Used for fuel, drawing, deodorant, filter, fertilizer etc.
Dye: Plants that provide dyes.
Wood: A list of the trees and shrubs that are noted for having useful wood.
Nitrogen Fixer: Plants that fix nitrogen in the soil
How it is grown
Prefers a heavy soil and a damp situation, but it succeeds in ordinary garden soil. Grows well in heavy clay soils. Thrives in drier soils than many members of this genus. Tolerates very infertile sites. This species has a symbiotic relationship with certain soil micro-organisms, these form nodules on the roots of the plants and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby. In garden design, as well as the above-ground architecture of a plant, root structure considerations help in choosing plants that work together for their optimal soil requirements including nutrients and water. The root pattern is branching: a heart root, dividing from the crown into several primary roots going down and out .
Propagating it: Seed - best sown in a cold frame as soon as it is ripe and only just covered. Spring sown seed should also germinate successfully so long as it is not covered. The seed should germinate in the spring as the weather warms up. When large enough to handle, prick the seedlings out into individual pots. If growth is sufficient, it is possible to plant them out into their permanent positions in the summer, otherwise keep them in pots outdoors and plant them out in the spring. If you have sufficient quantity of seed, it can be sown thinly in an outdoor seed bed in the spring. The seedlings can either be planted out into their permanent positions in the autumn/winter, or they can be allowed to grow on in the seed bed for a further season before planting them. Cuttings of mature wood, taken as soon as the leaves fall in autumn, outdoors in sandy soil.
Best place to grow: Woodland Garden Canopy; Bog Garden;
Habit: Tree
Hardiness: 4-8
Growth: Fast
Soil: Medium, heavy (clay)
Shade: Semi-shade, no shade
Moisture: Dry, moist, wet