Smooth Alder (Alnus serrulata): ID, Uses & Care

Want a tough, useful shrub for wet spots? Smooth alder is a fast-growing, nitrogen-fixing plant that stabilizes stream banks, feeds pollinators early in spring, and tolerates wet soils that many species hate. Below you'll find clear signs to ID it, how to use it in the landscape, and no-nonsense care tips so it thrives.

ID and habitat

Smooth alder usually grows as a large shrub or small tree up to 20 feet tall. Look for simple, toothed leaves 2–4 inches long that are glossy and bright green. The bark is smooth and gray when young, getting slightly furrowed with age. One giveaway: club-like catkins appear before or with the leaves — male catkins hang in clusters and release pollen, while smaller female cones follow and persist into winter.

It prefers wet or seasonally flooded areas: stream edges, marsh margins, and low spots in woodlands. You'll find it across eastern North America, especially in soils that are moist, acidic to neutral, and often poorly drained.

Planting, care, and practical uses

Plant smooth alder in full sun to light shade. It tolerates standing water better than most shrubs, so it's a go-to for shoreline and erosion-control work. Because it hosts nitrogen-fixing bacteria (Frankia) on its roots, it helps boost soil fertility nearby — useful when you want to nurse other plants into a wet site.

Propagation is straightforward: softwood cuttings in early summer root easily, and seeds can be sown in fall or stratified and started in spring. Space multiple plants 6–12 feet apart for a dense bank-stabilizing thicket, or plant single specimens where you want a small shade or screening tree.

Water well the first two seasons. After established, smooth alder needs little help, though it benefits from occasional pruning to remove dead stems and keep a tidy habit. Prune in late winter or early spring before new growth starts. It can sucker from the base; remove unwanted shoots to control spread.

Wildlife loves it. Early catkins feed bees and other pollinators, while dense shrubs offer nesting sites for birds. Fallen leaves and shaded banks create good habitat for aquatic life. The wood is not prized for fine carpentry but works for fuel and short-term structures.

Watch for common problems: leaf spots or rust can show up in wet summers, and occasional scale or borers may appear on older stems. Most issues are minor and manageable with good hygiene — remove infected branches and avoid overcrowding.

Looking to buy? Check native plant nurseries or conservation groups focused on watershed restoration. Ask for local provenance if you want plants well adapted to your region.

Got a wet, eroding spot or want a low-maintenance native that helps soil fertility? Smooth alder is a practical, underused choice. If you want, browse related guides on planting riparian buffers or contact us for sourcing tips and planting checklists.