Alnus glutinosa (Common Alder)


Botanical Information

FamilyBetulaceae
GenusAlnus
Speciesglutinosa
CategoryWoody
TypeTree (deciduous)
OriginIndigenous to Europe, western Asia and Northern Africa
Pronunciation

Details

USDA Hardiness Zone4a - 7a
USDA Hardiness Ref.
Canadian Hardiness Zone5a - 8a
Canada Hardiness Ref.
RHS Hardiness ZoneH7 - H4
RHS Hardiness Ref.
Temperature (°C)-34
Temperature (°F)-30
Height12 -18 m
Spread6 -12 m
GrowthMedium
Flowering PeriodApril

Description and Growing Information

General DescriptionOften shrubby in nature. Small trees usually pyramidal in shape. This species has been placed on the IUCN Red List as least concern.
ID CharacteristicLeaves toothed, about as long as broad, many of them with a shallow notch at the tip. Buds are purple.
LandscapePerhaps used for wet sites where not much else will grow. Alongside highways, in parks and other open areas. Does well in infertile areas and has the ability to fix atmospheric nitrogen.
PropagationSeed requires a cold period and 3 months at 5°C or autumn sowing should suffice if seed is placed in a coldframe.
CultivationTransplants readily; prefers moist or wet soil but performs well in dry soils as well. Tolerant of acid or slightly alkaline soils. Prune in winter or early spring.
PestsPowdery mildew attacks the female strobili but this is rarely serious. Cankers can be a problem. Woolly alder aphid, alder flea beetle, alder lace bug, leaf miner, sawfly and tent caterpillar.
Notable SpecimensNiagara Parks Botanical Gardens, Niagara Falls, Ontario, Canada. Whistling Gardens, Wilsonville, Ontario, Canada.
HabitatGrows along river and stream banks, marshy woods and woodlands.
Bark/Stem DescriptionYoung bark is often a lustrous grey-green or greenish brown and changes to polished brown with age.
Flower/Leaf Bud DescriptionStalked, 6 mm to 1.3 cm in length, reddish or reddish purple, appearing valvate.
Leaf DescriptionAlternate, simple, 5 - 10 cm long, 8 - 10 cm wide, oval of orbicular to suborbicular, rounded or emarginated at apex, usually broad cuneate, very gummy when young, coarsely and doubly serrate, dark green, glabrous.
Flower DescriptionMonoecious, reddish brown male flowers in 5-10 cm long catkins, 3-5 together; rather handsome but seldom noticed by most individuals; purplish females borne in a distinct egg-shaped strobile.
Fruit DescriptionNutlet, borne in persistent 8mm to 1.7 cm long ovoid strobile, on 3 mm to 2.5 cm long peduncles.
Colour DescriptionDark glossy green in summer, autumn colour does not occur as the leaves abscise green or brown.
Texture DescriptionMedium in leaf and in winter.

Photographs