Black alder is a medium short-lived deciduous tree in the birch family (Betulaceae) native to Europe, western Asia, and northern Africa. Early European colonists brought the black alder to North America where it was planted as an ornamental and to prevent erosion. The genus, Alnus , is Latin for alder. The species name, glutinosa , is reflective of the sticky texture of its young leaves and stems. This tree will grow 40-60 feet tall and 20-40 feet wide with strong branches. In its native habitat, it can reach 100 feet tall. The lower shaded branches wither and fall off leaving the tree with a small crown, especially in a woodland habitat. It does well in poor soils as it can fix nitrogen by forming a relationship with a nitrogen-fixing bacteria known as Frankia alni. Plant in full sun to partial shade in moist to occasionally wet soils. It can be identified by its glossy and toothed margined leaves, dangling catkins in the spring and cone-like fruits seen in the fall. The tree is found in wetlands, near ponds, lakes, and rivers. This tree is best used in sites that have poor soil or low-lying wet areas. It is used to improve the soil on recently cleared land. It is not ideal as a yard tree. Insects, Diseases, and Other Plant Problems: Alder aphids, lace bugs, flea beetle, tent caterpillars, and leaf miner are possible insect pests. Possible diseases include canker and powdery mildew. Black alder may sucker and form dense thickets.. In some states, it has spread aggressively to the detriment of native species and is considered a noxious weed. See native alternatives to the left. VIDEO created by Grant L. Thompson for “ Trees, Shrubs, and Woody Vines for Landscaping ” a plant identification course offered by the Department of Horticulture at Iowa State University .Black alder may sucker and form dense thickets.
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.
Fills a similar nicheAcer tataricum subsp. ginnalaBerberis thunbergii 'Atropurpurea'Lonicera fragrantissima
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
Clay; Loam (Silt); Sand
Soil pH
Acid (<6.0); Neutral (6.0-8.0)
Soil drainage
Good Drainage | Moist | Occasionally Wet
Available space
24-60 feet
NC region
Mountains; Piedmont
Mature size
Height: 40 ft. 0 in. - 60 ft. 0 in. | Width: 20 ft. 0 in. - 40 ft. 0 in.
Growth rate
Rapid
Maintenance
High
Canopy layer
1 - Canopy (>40 ft)
Form & Appearance
Habit / form
Multi-stemmed; Pyramidal
Texture
Medium
Foliage
Deciduous
Leaf color
Green
Leaf type
Simple
Leaf arrangement
Alternate
Leaf shape
Obovate; Orbicular
Leaf margin
Crenate; Dentate; Undulate
Leaf feel
Glossy
Leaf size
3-6 inches long, 3-6 inches wide
Hairs present
Yes
Leaf detail
Maximum leaf size is 5 inches long and 3 to 4 inches wide. Their shape is obovate or orbicular-obovate. The margins are crenate, dentate, and slightly undulated. The upper leaf surface is dark green and mostly smooth. The underside is a pale green and glabrous to slightly hairy along the leaf veins. The young leaf surface is heavily coated with resin. In the fall, the leaves will either remain green or turn brown. During the winter, the leaves may either drop off or wither on the tree.
Fall color
Brown/Copper; Insignificant
Flower color
Brown/Copper; Red/Burgundy
Flower form
Catkin; Insignificant
Flower size
< 1 inch
Flower detail
Male and female florets on the same tree. The male florets have clusters of 2-5 catkins that measure 2 to 3 inches long. They are reddish-brown, long, and drooping. The female florets are reddish-brown and have clusters of 2-5 cone-like catkins. Initially, they are only 1/4 inch long, but as they mature they measure 3/4 to 1 inch long and 1/2 inch wide. The blooming period occurs in early spring before the leaves emerge. The florets are cross-pollinated by the wind. After blooming the male catkins wither and fall away, but the female catkins remain on the tree through summer. In the fall, the female catkins release their seeds.
Bloom time
Spring
Fruit color
Black; Brown/Copper; Green
Fruit value
Long-lasting
Fruit size
< 1 inch long, < 1 inch wide
Fruit detail
Female catkins become hard and somewhat woody about 3/4 inches long. Inside are seeds that are released in the fall when they have matured. They remain on the tree through the winter months and into the next growing season.
Bark color
Dark Brown; Green; Light Brown; Light Gray
Bark detail
The bark on a mature tree is gray to brownish-gray. It is divided into flattened plates that are separated by shallow furrows. Young trees have light gray to greenish-gray bark.
Stem color
Brown/Copper; Gray/Silver
Stem detail
The stems are smooth and covered with glutinous glands. The stem color in winter is brown or gray.
Wildlife & Ecology
Native status
Non-native
Origin
Europe, northern Africa, western Asia
Distribution
Argentina; Azores; Chile; USA--CT, IL, IN, IA, KS, KY, MA, MI, MN, MO, MS, NJ, NY, OH, PA, RI, TN, VA, VT; WI; Ontario; New Zealand
Wildlife value
The tree provides food for deer, rabbits, and birds as well as offers shelter for nesting birds.
Attracts
Small Mammals; Songbirds
Food & Medicine
Harvest time
Fall
Uses (ethnobotany)
For many centuries in Europe, the Black Alder provided hardwood for timber. The wood was also used for carving, such as wooden shoes.