treeN. America Native

Grey Alder

The Story

Plant Bio

Alnus incana is a deciduous, multi-stemmed large shrub or medium tree native to the cooler regions of the Northern Hemisphere, where it thrives in wet, saturated soils. In early spring, before the foliage emerges, the branches hang with long, pendulous male catkins that shed wind-borne pollen.

The species features matte dark green, doubly serrated leaves with pale, sometimes downy undersides. It spreads via an extensive root system that produces vigorous suckers, readily forming dense thickets ideal for stabilizing banks.

Uses & Benefits:

Provides early spring interest with long, dangling male catkins before the leaves emerge.

Stabilizes wet banks and prevents soil erosion along waterways with its extensive, suckering root system.

Fixes atmospheric nitrogen to enrich poor soils and provides critical cover and browse for native wildlife.

Essentials

At a Glance

Plant Type

Tree

Height

480"

Width

240"

Light

Full Sun, Partial Sun

Zones

4, 5, 6

Water

High

Humidity

High

Lifespan

Moderate

Native To

Northern Hemisphere

Toxicity

Non-toxic

Bloom period

Early spring – Mid-spring

In flower about 2 months of the year

Planting

How to Grow

Select a planting site with full sun to partial shade and consistently moist, wet, or poorly drained soil.
Dig a hole twice as wide as the root ball and set the plant at the same depth it grew in the container.
Water thoroughly after planting and maintain consistent soil moisture, especially during dry spells.
Prune in late winter or early spring while dormant to remove dead wood or manage multi-stemmed growth.

Pro Tip

Avoid applying nitrogen fertilizer, as the root system hosts symbiotic Frankia bacteria that fix atmospheric nitrogen directly into the soil. Minimize root disturbance and heavy pruning near the base to prevent the rapid development of aggressive root suckers.

Keep It Thriving

Care Guide

Do

Plant in poorly drained, heavy clay, or seasonally flooded areas where other trees struggle.
Prune during the dormant winter period to shape the canopy and remove cankered wood.
Maintain high soil moisture levels, as the root system is highly susceptible to drought stress.

Don't

Do not apply nitrogen-heavy fertilizers, as the plant fixes its own nitrogen.
Do not plant in dry, sandy soils or areas prone to prolonged drought.
Do not prune heavily or disturb the soil around the root zone unless you want to stimulate sucker growth.

Seasonal Care Calendar

Task	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Mulch
Pest Check
Plant
Prune

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Wetland RestorationErosion ControlWindbreakNaturalized Areas

Companion Plants

Cornus sericea Betula nigra Carex stricta Salix nigra

Multiply

Propagation Methods

Good to Know

Common Questions

Grey Alder questions

What zones can Grey Alder grow in?

Grey Alder is hardy in USDA Zones 4–6. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

Is Grey Alder deer resistant?

Not reliably. Deer may browse Grey Alder, especially tender spring growth — plan on repellents or fencing where pressure is high.

When does Grey Alder bloom?

Grey Alder typically blooms in early spring through mid-spring. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.

Does Grey Alder need full sun?

Grey Alder does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.