Black Alder Alnus glutinosa
Other Common Name(s):
Previously known as:
- Alnus vulgaris
- Betula alnus var. glutinosa
- Betula glutinosa
- Phonetic Spelling
- AL-nus glu-ti-NO-sa
- Description
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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.
- Profile Video:
- See this plant in the following landscape:
- Cultivars / Varieties:
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- 'Aurea'
emerges with yellow leaves - 'Imperialis'
strongly dissected leaves - 'Laciniata'
shallowly dissected leaves - 'Pyramidalis'
narrower tree spread, resists disease
- 'Aurea'
- 'Aurea', 'Imperialis', 'Laciniata', 'Pyramidalis'
- Tags:
- Cultivars / Varieties:
-
- 'Aurea'
emerges with yellow leaves - 'Imperialis'
strongly dissected leaves - 'Laciniata'
shallowly dissected leaves - 'Pyramidalis'
narrower tree spread, resists disease
- 'Aurea'
- 'Aurea', 'Imperialis', 'Laciniata', 'Pyramidalis'
- Tags:
-
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Attributes:
- Genus:
- Alnus
- Species:
- glutinosa
- Family:
- Betulaceae
- 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.
- Life Cycle:
- Woody
- Recommended Propagation Strategy:
- Seed
- Country Or Region Of 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.
- Particularly Resistant To (Insects/Diseases/Other Problems):
- Tough adaptable plant; few pest problems; tolerates short term flooding; easy to transplant; wet, infertile, or dry soil
- Dimensions:
- Height: 40 ft. 0 in. - 60 ft. 0 in.
- Width: 20 ft. 0 in. - 40 ft. 0 in.
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Whole Plant Traits:
- Plant Type:
- Tree
- Woody Plant Leaf Characteristics:
- Deciduous
- Habit/Form:
- Multi-stemmed
- Pyramidal
- Growth Rate:
- Rapid
- Maintenance:
- High
- Texture:
- Medium
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Cultural Conditions:
- 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 Texture:
- Clay
- Loam (Silt)
- Sand
- Soil pH:
- Acid (<6.0)
- Neutral (6.0-8.0)
- Soil Drainage:
- Good Drainage
- Moist
- Occasionally Wet
- Available Space To Plant:
- 24-60 feet
- NC Region:
- Mountains
- Piedmont
- USDA Plant Hardiness Zone:
- 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b
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Fruit:
- Fruit Color:
- Black
- Brown/Copper
- Green
- Fruit Value To Gardener:
- Long-lasting
- Display/Harvest Time:
- Fall
- Fruit Length:
- < 1 inch
- Fruit Width:
- < 1 inch
- Fruit Description:
- 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.
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Flowers:
- Flower Color:
- Brown/Copper
- Red/Burgundy
- Flower Inflorescence:
- Catkin
- Insignificant
- Flower Bloom Time:
- Spring
- Flower Size:
- < 1 inch
- Flower Description:
- 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.
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Leaves:
- Woody Plant Leaf Characteristics:
- Deciduous
- Leaf Color:
- Green
- Leaf Feel:
- Glossy
- Deciduous Leaf Fall Color:
- Brown/Copper
- Insignificant
- Leaf Type:
- Simple
- Leaf Arrangement:
- Alternate
- Leaf Shape:
- Obovate
- Orbicular
- Leaf Margin:
- Crenate
- Dentate
- Undulate
- Hairs Present:
- Yes
- Leaf Length:
- 3-6 inches
- Leaf Width:
- 3-6 inches
- Leaf Description:
- 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.
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Bark:
- Bark Color:
- Dark Brown
- Green
- Light Brown
- Light Gray
- Surface/Attachment:
- Furrowed
- Bark Plate Shape:
- Irregular
- Bark Description:
- 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.
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Stem:
- Stem Color:
- Brown/Copper
- Gray/Silver
- Stem Is Aromatic:
- No
- Stem Lenticels:
- Not Conspicuous
- Stem Surface:
- Smooth (glabrous)
- Stem Description:
- The stems are smooth and covered with glutinous glands. The stem color in winter is brown or gray.
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Landscape:
- Landscape Location:
- Pond
- Riparian
- Landscape Theme:
- Rain Garden
- Winter Garden
- Design Feature:
- Barrier
- Attracts:
- Small Mammals
- Songbirds
- Resistance To Challenges:
- Dry Soil
- Wet Soil
- Problems:
- Short-lived
- Weedy
