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Black Alder Alnus glutinosa

Other Common Name(s):

Other plants called Black Alder:

Previously known as:

  • Alnus vulgaris
  • Betula alnus var. glutinosa
  • Betula glutinosa
Phonetic Spelling
AL-nus glu-ti-NO-sa
Description

Black alder is a medium-sized deciduous tree in the Betulaceae (birch) family native to Europe, western Asia, and northern Africa. Early colonists from Europe 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 is readily identifiable by its glossy and toothed margined leaves as well as by its dangling catkins seen in the spring and cone-like fruits seen in the fall. The tree is often found growing in wetlands, as well as near ponds, lakes, and rivers. It is used to improve the soil on recently cleared land. The tree roots can add nitrogen to the soil by forming a relationship with a nitrogen-fixing bacteria known as Frankia alni. 

This tree is best used in sites that have poor soil or low-lying wet areas. It is fast-growing but unlike the silver maple, which is also fast-growing and prone to weak wood, the black alder's branches are stronger.

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. It can spread aggressively. In western NC, this species has been known to spread aggressively into areas where habitat restoration has taken place, sometimes to the detriment of native species. 

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:
  • 'Aurea'
    emerges with yellow leaves
  • 'Imperialis'
    strongly dissected leaves
  • 'Laciniata'
    shallowly dissected leaves
  • 'Pyramidalis'
    narrower tree spread, resists disease
'Aurea', 'Imperialis', 'Laciniata', 'Pyramidalis'
Tags:
#deciduous#full sun tolerant#winter interest#fast growing#aggressive#multistemmed#pest resistant#transplant#glossy leaves#wind pollinated#wet soils tolerant#dry soils tolerant#partial shade tolerant#flood tolerant#medium size tree#weed#landscape plant sleuths course
 
Cultivars / Varieties:
  • 'Aurea'
    emerges with yellow leaves
  • 'Imperialis'
    strongly dissected leaves
  • 'Laciniata'
    shallowly dissected leaves
  • 'Pyramidalis'
    narrower tree spread, resists disease
'Aurea', 'Imperialis', 'Laciniata', 'Pyramidalis'
Tags:
#deciduous#full sun tolerant#winter interest#fast growing#aggressive#multistemmed#pest resistant#transplant#glossy leaves#wind pollinated#wet soils tolerant#dry soils tolerant#partial shade tolerant#flood tolerant#medium size tree#weed#landscape plant sleuths course
  • 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.
  • Whole Plant Traits:
    Plant Type:
    Tree
    Woody Plant Leaf Characteristics:
    Deciduous
    Habit/Form:
    Multi-stemmed
    Pyramidal
    Growth Rate:
    Rapid
    Maintenance:
    Low
    Texture:
    Medium
  • 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
    USDA Plant Hardiness Zone:
    4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b
  • Fruit:
    Fruit Color:
    Black
    Brown/Copper
    Green
    Fruit Value To Gardener:
    Long-lasting
    Display/Harvest Time:
    Fall
    Fruit Type:
    Samara
    Fruit Length:
    < 1 inch
    Fruit Width:
    < 1 inch
    Fruit Description:
    Female catkins develop into wood cones about 3/4 inches long. Inside the cones are winged seeds that are released in the fall when they have matured. The cones remain on the tree through the winter months and into the next growing season.
  • Flowers:
    Flower Color:
    Brown/Copper
    Red/Burgundy
    Flower Inflorescence:
    Catkin
    Insignificant
    Flower Value To Gardener:
    Showy
    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.
  • 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. Parasites may occur such as Dasineura tortilis or Aceria nalepai.
  • 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.
  • 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.
  • Landscape:
    Landscape Location:
    Coastal
    Pond
    Riparian
    Landscape Theme:
    Rain Garden
    Winter Garden
    Design Feature:
    Barrier
    Attracts:
    Small Mammals
    Songbirds
    Resistance To Challenges:
    Dry Soil
    Wet Soil
    Problems:
    Weedy