Speckled alder

The speckled alder, Alnus incana subsp. rugosa (formerly Alnus rugosa), is a shrub or small tree native to much of Canada, including Quebec. It is a very ecologically useful species and particularly adapted to wet ground.

Description

• Height: generally 3 to 10 meters.
• Width: 2 to 6 meters.
• Habit: often multi-trunked, upright, and irregular.
• Growth: rapid.

Its name comes from the slightly rough texture of its leaves, especially on their underside.

Foliage

• Oval to elliptical leaves.
• Dark green on top.
• Underside paler and slightly fuzzy.
• Subtle autumn color, generally yellow.

It is not a species sought after for its autumn colors, but rather for its robustness and ecological interest.

Flowering and fruits

Like other alders:

• It produces elongated male catkins that appear before the leaves in spring.
• Female flowers become small, woody, dark brown cones that often persist throughout winter.

These cones are quite decorative and allow the species to be identified even in winter.

A champion of wet soils

Speckled alder excels where many other trees fail:

• Stream banks.
• Ditches.
• Swamps.
• Poorly drained areas.
• Areas subject to temporary flooding.

It even tolerates poor and acidic soils.

A plant that enriches the soil

Like several alder species, it lives in symbiosis with bacteria of the genus Frankia that fix atmospheric nitrogen.

Result:

• it naturally enriches the soil with nitrogen;
• it gradually improves degraded land;
• it promotes the establishment of other plants.

This is a rather rare characteristic among the trees in our regions.

Interest for wildlife

Speckled alder is very valuable for biodiversity:

• The seeds feed several granivorous birds.
• The catkins provide an early source of pollen.
• Dense stands offer shelter and protection to many animals.
• Its roots help stabilize banks and limit erosion.

Hardiness

• Zone 2 to 6.
• Extremely hardy.
• Perfectly adapted to Shawinigan and the entire Mauricie region.

Use in the garden

It is rarely used as a classic ornamental tree, but it is excellent for:

• naturalistic gardens;
• ecological restoration projects;
• riparian strips;
• difficult wet areas;
• natural windbreaks.