TREES & plants

Seaside alder

Seaside alder in winter.

Seaside alder is a fast-growing native tree. It stays short enough to be used under utility lines, but may be difficult to locate in local nurseries.

Botanical name: 
Alnus maritima
All Common Names: 
seaside alder, brook alder
Family (English): 
Family (Botanic): 
Tree or Plant Type: 
  • Tree
  • Deciduous (seasonally loses leaves)
Native Locale: 
  • North America
Planting Site: 
  • Residential and parks, 
  • City parkway, 
  • Wide median, 
  • Under utility lines
Landscape Uses: 
  • Utility, 
  • Specimen, 
  • Parkway/street
Size Range: 
  • Medium tree (25-40 feet), 
  • Small tree (15-25 feet)
Mature Height: 
20-30 feet
Mature Width: 
16-20 feet
Light Exposure: 
  • Full sun (6 hrs direct light daily), 
  • Partial sun/shade (4-6 hrs light daily)
Hardiness Zones: 
  • Zone 4, 
  • Zone 5 (Chicago), 
  • Zone 6, 
  • Zone 7
Soil Preference: 
  • Moist, well-drained soil, 
  • Wet soil
Acid Soils: 
  • Tolerant
Alkaline Soils: 
  • Tolerant
Salt Spray: 
  • Intolerant
Soil Salt: 
  • Intolerant
Drought Conditions: 
  • Moderately Tolerant
Poor Drainage: 
  • Prefers
Planting Considerations: 
  • Intolerant of pollution, 
  • May be difficult to find in nurseries
Ornamental Interest: 
  • Fall color, 
  • Persistent fruit/seeds
Season of Interest: 
  • Early fall
Flower Color & Fragrance: 
  • Yellow
Shape or Form: 
  • Pyramidal
Growth Rate: 
  • Fast
  • Nesting birds
More Information: 

Tree & Plant Care

This species is best in moist to wet sites and is able to tolerate short-term flooding.

Disease, pests, and problems

Potential problems include cankers, alder aphids, and leaf miners.

Native geographic location and habitat

Native to the United States.  Generally found in wet locations.

Bark color and texture 

Bark is light brown to reddish brown and may be mottled.

Leaf or needle arrangement, size, shape, and texture

Simple, alternate leaves are oblong to egg-shaped with finely toothed margins.  Leaves are dark green in summer, changing to yellow-brown in fall.

Flower arrangement, shape, and size

Male and female flowers on the same tree but in separate structures (monoecious). Male catkins flower in fall.

Fruit, cone, nut, and seed descriptions

Fruit are cone-like structures.



Alnus maritima or Seaside alder