Japanese Alder

Alnus japonica

Native to:
China, Japan, Korea, Kuril Is., Russia, Taiwan

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Taxonomy

Division:
Magnoliophyta | - Flowering plants
Family:
Betulaceae
Genus:
Alnus
Species:
Alnus japonica
USDA Symbol:
ALJA8

Growth Characteristics

Height:
2000 cm
Light Requirements:
Full Sun
Drought Tolerance:
Low
Bloom Months:
mar,apr

Keystone Species Ranking

Caterpillar Keystone:
★★★★★ Butterfly & moth species supported by this genus (NWF)

Garden & Ecology Notes

Wildlife Value:
birds, small mammals
Fall Color:
yellow

Soil Requirements

Soil Type:
rich, well-drained loamy soil
pH:
5.5 - 7.5 (slightly acidic to neutral)
Drainage:
tolerates poor drainage
Moisture:
consistently moist
Notes:
Commonly found in riparian zones and wetlands

Propagation & Germination

Stratification:
Cold/moist stratification required — 30–60 days
Germination Time:
14–30 days
Notes:
Seeds require light for germination. Fresh seed germinates best; viability decreases with storage.

The above propagation data sourced from Claude AI

ORGHPS Germination Guide: Sow @ 20C. Germinates within 3 months. Requires light / surface sow (fine seed).

Source: Ontario Rock Garden & Hardy Plant Society