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Japanese Alder

Alnus japonica (AL-nus juh-PON-ih-kuh)

Family: Betulaceae Non-native Understory (15-40 ft)

Tough, adaptable plant; few pest problems; tolerates short-term flooding; flower and fruiting best in full sun. Uncommon in the U.S. Good selection for difficult sites such as moist low spots or dry sites with poor soils. Woodland areas. Does not perform well south of zone 7. Insects, Diseases, and Other Plant Problems: No serious problems.

Source: NC State Extension Gardener Plant Toolbox ↗ NC State Extension Gardener Plant Toolbox, 37 attributes.

How it fits the guild

Guild layer 2 - Understory (15-40 ft)
See companions & conflicts ↓

Companions & Conflicts

Curated pairwise relationships between this plant and others in the library — who feeds whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.

No curated interactions recorded for this species yet.

Also noted by NC State

Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.

Full plant profile

Growing Conditions
Plant type
Tree
Life cycle
Woody
USDA zones
5a, 5b, 6a, 6b, 7a, 7b
Light
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil drainage
Frequent Standing Water
Available space
6-feet-12 feet; 12-24 feet
Mature size
Height: 12 ft. 0 in. - 25 ft. 0 in. | Width: 8 ft. 0 in. - 12 ft. 0 in.
Maintenance
Low
Canopy layer
2 - Understory (15-40 ft)
Form & Appearance
Habit / form
Pyramidal
Texture
Medium
Foliage
Deciduous
Leaf color
Green
Leaf shape
Elliptical; Ovate
Leaf margin
Serrate
Leaf size
3-6 inches long
Hairs present
No
Leaf detail
Oval, narrow leaves acuminate, serrulate, dark green leaves (to 5" long). Wedge-shaped at the base and light green underneath. Fall color unremarkable.
Flower color
Brown/Copper; Gold/Yellow; Insignificant; Purple/Lavender
Flower form
Catkin
Flower detail
Monecious blooms appear in March yellow-brown to red-brown catkins (male flowers) appear in clusters, female flowers on short, purplish-brown strobili which persist until winter
Bloom time
Spring
Fruit type
Nut
Fruit size
< 1 inch long
Fruit detail
ellipsoidal fruiting cones 3/4"-1" long
Wildlife & Ecology
Native status
Non-native
Origin
Japan, Korea, Manchuria
Food & Medicine
Fruit type
Nut
Landscape Use
Landscape location
Slope/Bank; Woodland
Design feature
Shade Tree
Garden tags
#deciduous #conical #adaptable #shade tree #moist soil #pryamidal #dry soils tolerant #wet soils tolerant #spotted leaves #woodland
Problems & Resistance
Resistant to
Dry Soil; Insect Pests; Poor Soil; Wet Soil

Planted at Hunnicutt

Nobody’s planted this one yet.