Logo

TREES & Plants

Black alder

This tree is invasive and should not be planted. Growing 40 to 60 feet tall, black alder is typically tall and narrow but sometimes pyramid-shaped. It can be identified by its large, glossy green, oval to round leaves with a toothed margin; dangling catkins, or long, bushy flowers, in early spring; and egg-shaped nutlets, somewhat resembling cones, in fall. Young leaves and shoots are often sticky from a resin. The seed are dispersed by wind and, if they fall on water, can be spread for long distances. Along stream beds and in other wet areas, it can form dense groves that displace native plants. Like members of the bean family, it can fix nitrogen from the air, allowing it to colonize very poor soils. It invades woodlands and wetlands such as forest preserves where it disrupts the forest ecosystem by preventing the growth of understory shrubs and other plants. The tree was brought from Europe to the East Coast by early colonists. The Morton Arboretum recommends that this species not be planted and that it be removed where possible. 

Botanical name: 
Alnus glutinosa
All Common Names: 
Black alder, European alder
Family (English): 
Birch
Family (Botanic): 
Betulaceae
Tree or Plant Type: 
  • Tree
Foliage: 
  • Deciduous (foliage falls off)
Native Locale: 
  • Non-native
Hardiness Zones: 
  • Zone 5
  • Zone 6
  • Zone 7
  • Zone 8
  • Zone 9
Growth Rate: 
  • Fast
Light Exposure: 
  • Full sun (6 hrs direct light daily)
Tolerances: 
  • Wet sites
  • Occasional flooding
Soil Preference: 
  • Wet soil
Flower Color & Fragrance: 
  • Yellow
Size Range: 
  • Large tree (more than 40 feet)
Shape or Form: 
  • Narrow
  • Pyramidal
  • Upright
More Information: 

Size

40 to 60 feet high and 20 to 25 feet wide

 

 

Native geographic location and habitat

Europe and central Asia

 

Bark color and texture 

Light to greenish gray

 

Leaf or needle arrangement, size, shape, and texture

Leaves oval to rounded, glossy green, with a toothed margine. Young leaves and shoots often sticky from a resin

 

Flower arrangement, shape, and size

Dangling catkins, yellow-red, in early spring before leaves appear

 

Fruit, cone, nut, and seed descriptions

Egg-shaped nutlets, resembling cones, in fall