Alnus maritima

Common Names

Seaside Alder, Brook Alder

Summary

Seaside alder is a deciduous shrub or small tree native to North-Central and Southeastern United States, with disjunct populations in Oklahoma, Georgia, Delaware, and Maryland. It typically forms multi-stemmed clumps to 20–30 ft tall and 16–30 ft wide, grows in wet soils by ponds, swamps, and streams, and features autumn flowering with yellow catkins and slender, serrated leaves. Smooth light gray bark and nitrogen-fixing root nodules are distinctive. In cultivation, seaside alder favors full sun to part shade and moist or wet sites, tolerating heavy soils and damp conditions, hardy in USDA zones 4–7, it suits rain gardens, riparian plantings, hedges, windbreaks, or as a specimen plant and provides wildlife habitat. Propagation occurs by seed, which requires cold stratification for germination in spring, and by cuttings of mature wood taken in autumn for vegetative propagation, and it is commonly used in restoration and ornamental plantings.

Lifecycle

Perennial

Height

240-360 inches

Spread

16-29 feet

Hardiness Zones

Zones 4-7

Sunlight Requirements

Ideally Full Sun to Partial Shade; not suitable in Full Shade.

Soil Type

Moist, well-drained soil; tolerates wet soil.

Soil Drainage

Moist to wet soils, including standing water and poorly drained conditions.

Soil pH

6.0-7.0, slightly acidic to neutral, tolerates acidic and alkaline soils

Bloom Color

Insignificant

Bloom Time

Fall (late summer to early fall)

Foliage Color

Dark green in summer; turns yellow-brown in fall.

Fall Foliage Color

Green

Leaf Lifecycle

Deciduous

Growth Rate

Moderate

Seasons of Interest

Summer and Fall

Propagation Methods

Seeds, Rooted Cuttings, Air Layering, Grafting

Attracts Wildlife

Attracts birds