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Alnus maritima

Common Name(s):

Previously known as:

  • Alnus metoporina
Description

Seaside alder is a deciduous small tree or large shrub in the Betulaceae (birch) family. 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 “Trees, Shrubs, and Woody Vines for Landscaping” a plant identification course offered by the Department of Horticulture at Iowa State University.

Profile Video:
See this plant in the following landscape:
Cultivars / Varieties:
  • Alnus maritima subsp. oklahomensis 'September Sun'
    oklahomensis is noted for green foliage and vigor; 'September Sun' grows rapidly with dense foliage.
Alnus maritima subsp. oklahomensis 'September Sun'
Tags:
#small tree#rain garden#specimen#shrub#deciduous shrub#riparian#windbreak#standing water tolerant#hedges#moist soil#salt spray tolerant#large shrub#naturalized area#nesting sites#deciduous tree#wet soils tolerant#clay soils tolerant#bird friendly#woodland garden#coastal#landscape plant sleuths course
 
Cultivars / Varieties:
  • Alnus maritima subsp. oklahomensis 'September Sun'
    oklahomensis is noted for green foliage and vigor; 'September Sun' grows rapidly with dense foliage.
Alnus maritima subsp. oklahomensis 'September Sun'
Tags:
#small tree#rain garden#specimen#shrub#deciduous shrub#riparian#windbreak#standing water tolerant#hedges#moist soil#salt spray tolerant#large shrub#naturalized area#nesting sites#deciduous tree#wet soils tolerant#clay soils tolerant#bird friendly#woodland garden#coastal#landscape plant sleuths course
  • Attributes:
    Genus:
    Alnus
    Species:
    maritima
    Family:
    Betulaceae
    Life Cycle:
    Woody
    Country Or Region Of Origin:
    United States
    Distribution:
    DE, GA, MD, OK
    Wildlife Value:
    Nesting site for birds.
    Dimensions:
    Height: 20 ft. 0 in. - 30 ft. 0 in.
    Width: 16 ft. 0 in. - 29 ft. 0 in.
  • Whole Plant Traits:
    Plant Type:
    Shrub
    Tree
    Woody Plant Leaf Characteristics:
    Deciduous
    Habit/Form:
    Multi-stemmed
    Multi-trunked
    Pyramidal
    Rounded
    Growth Rate:
    Medium
    Maintenance:
    Medium
  • Cultural Conditions:
    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 To Plant:
    12-24 feet
    24-60 feet
    USDA Plant Hardiness Zone:
    3b, 3a, 4a, 4b, 5b, 5a, 6b, 6a, 7b, 7a
  • Fruit:
    Fruit Color:
    Brown/Copper
    Green
    Display/Harvest Time:
    Spring
    Summer
    Fruit Length:
    1-3 inches
    Fruit Width:
    1-3 inches
    Fruit Description:
    Small upright cones in spring and summer.
  • Flowers:
    Flower Color:
    Gold/Yellow
    Green
    Purple/Lavender
    Red/Burgundy
    Flower Inflorescence:
    Catkin
    Insignificant
    Flower Bloom Time:
    Fall
    Summer
    Flower Size:
    1-3 inches
    Flower Description:
    Produces insignicant blooms from late summer to early fall.
  • Leaves:
    Woody Plant Leaf Characteristics:
    Deciduous
    Leaf Color:
    Green
    Leaf Feel:
    Glossy
    Leathery
    Deciduous Leaf Fall Color:
    Insignificant
    Leaf Type:
    Simple
    Leaf Arrangement:
    Alternate
    Leaf Shape:
    Elliptical
    Oblong
    Obovate
    Ovate
    Leaf Margin:
    Serrate
    Hairs Present:
    No
    Leaf Length:
    1-3 inches
    Leaf Width:
    1-3 inches
  • Bark:
    Bark Color:
    Light Gray
    Surface/Attachment:
    Smooth
    Bark Description:
    Light gray, smooth bark.
  • Stem:
    Stem Color:
    Brown/Copper
    Red/Burgundy
    Stem Is Aromatic:
    No
    Stem Bud Scales:
    Enclosed in 2 scales
    Stem Lenticels:
    Not Conspicuous
    Stem Surface:
    Smooth (glabrous)
    Stem Description:
    Hairy (pubescent) when young, Smooth (glabrous)
  • Landscape:
    Landscape Location:
    Naturalized Area
    Riparian
    Woodland
    Landscape Theme:
    Rain Garden
    Water Garden
    Design Feature:
    Hedge
    Small Tree
    Specimen
    Attracts:
    Songbirds
    Resistance To Challenges:
    Drought
    Erosion
    Poor Soil
    Wet Soil
    Wind