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 toothed margins. The tree has dangling catkins in early spring and cone-like fruits in fall. Young leaves and shoots are often sticky from 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 wetlands and woodlands, 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.
- Family (English) Birch
- Family (botanic) Betulaceae
- Tree or plant type Tree
- Foliage Deciduous (seasonally loses leaves)
- Native locale Non-native
- Size range Large tree (more than 40 feet)
- Mature height 40-60 feet
- Mature width 20-40 feet
- Light exposure Full sun (6 hrs direct light daily), Partial sun / shade (4-6 hrs light daily)
- Hardiness zones Zone 4, Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7
- Soil preference Wet soil
- Tolerances clay soil, Occasional flooding, Wet sites
- Flower color and fragrance Inconspicuous
- Shape or form Pyramidal
- Growth rate Fast
- Transplants well Yes
- Planting considerations Excessive sucker growth
- Wildlife Nesting birds, Seed-eating birds, Small mammals
- Has cultivars Yes
