TREES & plants

European black alder

European black alders have invasive traits that enable it to spread aggressively. This tree is under observation and may be listed on official invasive species lists in the near future. Review of risks should be undertaken before selecting this tree for planting sites. 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. 

Botanical name: 
Alnus glutinosa
All Common Names: 
Black alder, European alder
Family (English): 
Family (Botanic): 
Tree or Plant Type: 
  • Tree
  • Deciduous (seasonally loses leaves)
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)
  • 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: 


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