European black alder has 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 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.
- Large tree (more than 40 feet)
- Full sun (6 hrs direct light daily)
- Partial sun/shade (4-6 hrs light daily)
- Zone 4
- Zone 5
- Zone 6
- Zone 7
- Wet soil
- Moderately Tolerant
- Excessive sucker growth
- Deciduous (seasonally loses leaves)
- Persistent fruit/seeds
- Attractive bark
- Nesting birds
- Seed-eating birds
- Small mammals
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 margin. Young leaves and shoots often sticky from a resin.
Flower arrangement, shape, and size
Male flowers in dangling catkins, yellow-red, in early spring before leaves appear. Female flowers small, pink, egg-shaped.
Fruit, cone, nut, and seed descriptions
Egg-shaped nutlets, resembling cones, in fall.