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Beach alder

Alnus maritima (ALL-nus mah-RI-tee-mah)

Family: Betulaceae Native Understory (15-40 ft)

Seaside alder is a deciduous small tree or large shrub in the birch family (Betulaceae). Native only to three small disjunctive populations, with each classified as a separate subspecies (subspecies maritima in the coastal plains of Southern Delaware and the eastern shore of Maryland, subspecies georgiensis in northwest Georgia, and subspecies oklahomensis in south-central Oklahoma). In nature, it is often found growing beside streams and ponds near coastal areas and sometimes in standing water, making it well-suited to wet soils or areas with seasonal flooding. The genus name is Latin for alder and the species name comes from the Latin "growing by the sea". Growing at a medium rate it reaches a mature height of 20 to 30 feet tall and 16 to 30 feet wide, Thriving in part shade as well as sun, seaside alder tolerates clay and alkaline soils, and is somewhat drought tolerant once established. It also tolerates saline soils, but will not do well in full shade. Its dense deciduous foliage is attractive to nesting birds and makes it suitable as a windscreen, hedges, or specimen plant. It is also known for its ability to fix nitrogen in the soil. Other landscape uses include rain gardens, riparian, and naturalized areas, especially those with wet soils. Insects, Diseases, and Other Plant Problems: No serious problems. VIDEO created by Grant L. Thompson for β€œ Trees, Shrubs, and Woody Vines for Landscaping ” a plant identification course offered by the Department of Horticulture at Iowa State University .

Source: NC State Extension Gardener Plant Toolbox ↗ NC State Extension Gardener Plant Toolbox, 60 attributes.

How it fits the guild

Guild layer 2 - Understory (15-40 ft) Optimal soil pH Acid (<6.0); Alkaline (>8.0); Neutral (6.0-8.0)
See companions & conflicts ↓

Companions & Conflicts

Curated pairwise relationships between this plant and others in the library — who feeds whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.

No curated interactions recorded for this species yet.

Also noted by NC State

Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.

Full plant profile

Growing Conditions
Plant type
Shrub; Tree
Life cycle
Woody
USDA zones
3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b
Light
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
Clay; Loam (Silt)
Soil pH
Acid (<6.0); Alkaline (>8.0); Neutral (6.0-8.0)
Soil drainage
Frequent Standing Water | Moist | Occasional Flooding | Occasionally Wet
Available space
12-24 feet; 24-60 feet
Mature size
Height: 20 ft. 0 in. - 30 ft. 0 in. | Width: 16 ft. 0 in. - 29 ft. 0 in.
Growth rate
Medium
Maintenance
Medium
Canopy layer
2 - Understory (15-40 ft)
Form & Appearance
Habit / form
Multi-stemmed; Multi-trunked; Pyramidal; Rounded
Foliage
Deciduous
Leaf color
Green
Leaf type
Simple
Leaf arrangement
Alternate
Leaf shape
Elliptical; Oblong; Obovate; Ovate
Leaf margin
Serrate
Leaf feel
Glossy; Leathery
Leaf size
1-3 inches long, 1-3 inches wide
Hairs present
No
Fall color
Insignificant
Flower color
Gold/Yellow; Green; Purple/Lavender; Red/Burgundy
Flower form
Catkin; Insignificant
Flower size
1-3 inches
Flower detail
Produces insignicant blooms from late summer to early fall.
Bloom time
Fall; Summer
Fruit color
Brown/Copper; Green
Fruit size
1-3 inches long, 1-3 inches wide
Fruit detail
Small upright cones in spring and summer.
Bark color
Light Gray
Bark detail
Light gray, smooth bark.
Stem color
Brown/Copper; Red/Burgundy
Stem detail
Hairy (pubescent) when young, Smooth (glabrous)
Wildlife & Ecology
Native status
Native
Origin
United States
Distribution
DE, GA, MD, OK
Wildlife value
Nesting site for birds.
Attracts
Songbirds
Food & Medicine
Harvest time
Spring; Summer
Landscape Use
Landscape location
Naturalized Area; Riparian; Woodland
Landscape theme
Rain Garden; Water Garden
Design feature
Hedge; Small Tree; Specimen
Garden tags
#moist soil #clay soils tolerant #standing water tolerant #salt spray tolerant #windbreak #small tree #shrub #landscape plant sleuths course #riparian #wet soils tolerant #deciduous shrub #specimen #deciduous tree #naturalized area #bird friendly #large shrub #rain garden #hedge #coastal plant #woodland #nesting site
Problems & Resistance
Resistant to
Drought; Erosion; Poor Soil; Wet Soil; Wind

Planted at Hunnicutt

Nobody’s planted this one yet.