Image for Thin Leaf Alder

Thin Leaf Alder

Scientific name

Alnus incana subsp tenuifolia


The Thin Leaf Alder is a small, deciduous tree species that can grow from 6-12 m in height. This species may also be known by the common names Mountain Alder or River Alder. The bark is grayish brown, thin and smooth, becoming reddish and scaly with age. The leaves are dark green in colour, 5-10 cm long, oval shaped, and have doubly serrated margins. This tree produces catkins in March and April, which are cylinder shaped clusters of flowers. In the fall, cone like fruits are developed, which contain tiny, winged samara seeds and are dispersed by wind. Thin Leaf Alder is an early colonizer species so it is fast growing, short lived, and produces lots of leaf debris. This tree has an extensive, shallow root system making it useful for quickly controlling erosion and stabilizing shorelines. It is also able to fix atmospheric nitrogen and convert it into a usable nutrient, thus may be useful for establishing plants on nutrient poor sites. The seeds, buds, and catkins of Thin Leaf Alder are a good food source for many bird species, including Goldfinches and Chickadees.

Planting conditions

Thin Leaf Alder grows best in wet or moist soils with full or partial sun exposure. This tree can tolerate a range of soil types and can grow in nutrient poor soil. It is very tolerant of the cold and considered a winter hardy plant. It can also tolerate periodic flooding but not drought so should be watered if in dry conditions. This tree is naturally found in moist mountains, swamps, bogs, fens, wet forests, and along river or lake shorelines.


  • Plant height:
    • Any
    • Over 3m
  • Moisture level:
    • Moist
    • Wet
    • Flood Tolerant
  • Light conditions:
    • Full sun
    • Partial sun
  • Soil type:
    • Sandy
    • Loamy
    • Clay
    • Humus
    • Rocky
  • pH:
    • Acidic
    • Basic
    • Normal
  • Depth:
    • Potted
  • Eco Zone:
    • 1a
    • 1b
    • 2a
    • 2b
    • 3a
    • 3b
    • 4a
    • 4b
    • 5a
    • 5b
  • Plant type:
    • Tree
  • Height:
    • 6-12 m
  • Spread:
    • 2 m