What are the best conditions for Alnus glutinosa?

It thrives in moist to wet soils and full sun to partial shade.

How fast does it grow?

It's a relatively fast-growing tree, especially in ideal conditions.

Can it tolerate flooding?

Yes, it is very tolerant of waterlogged soils and periodic flooding.

When does it flower and produce seeds?

It flowers in early spring, and its cone-like fruits mature in the fall.

Plant guide

Common Alder.

Alnus glutinosa

Pronounced AL-nus gloo-TIN-oh-sa

Also known as Alder, Black Alder, Black Elder, Common alder, European Alder, European black alder

Common Alder is a fast-growing deciduous tree native to Europe, North Africa, and parts of Asia. It's often found in wet areas like riverbanks and marshes, where its roots help stabilize the soil. This tree is known for its nitrogen-fixing capabilities, enriching the soil around it.

At a glance

Care level: Easy
Plant type: Deciduous tree
Light: Full sun to partial shade
Indoor light: bright-indirect
Water: Every 1 to 7 days
Mature size: Up to 25m tall and 15m wide
Growth rate: fast
Hardiness: USDA 3 to 8
Bloom time: Early spring

Care

Common Alder thrives in moist to wet conditions and tolerates a wide range of soil types, though it prefers slightly acidic to neutral pH. It can handle full sun to partial shade. Pruning is generally minimal, mainly for shaping or removing dead branches.

Watering: Keep soil consistently moist, especially when young. Tolerates waterlogged conditions.
Feeding: Generally not needed due to nitrogen fixation, but a balanced fertilizer in spring can help establish young trees.
Pruning: Prune in late winter or early spring to remove dead, damaged, or crossing branches. Can be pruned for shape.
Repotting: Mature trees rarely need repotting; young trees may benefit from repotting every 5-10 years if root-bound.
Soil: Prefers moist, well-drained soil; tolerates clay and wet conditions
Soil pH: 4.5 to 7.5
Temperature: -30 to 30°C
Humidity: 60 to 90%
Drought tolerance: Low
Lifespan: Perennial, typically 60 to 100 years
Deer and rabbits: Moderate; young trees may be browsed by deer and rabbits, especially when other food is scarce.

Signs it needs repotting

Roots circling densely around the inside of the pot.
Water drains very slowly or not at all.
Plant growth appears stunted despite adequate watering.
Visible roots emerging from drainage holes.

Safety

People: This plant is not considered toxic to humans.
Children: No specific safety concerns for children beyond typical outdoor plant handling.
Contact allergens: Sap may cause mild skin irritation in sensitive individuals.
Airborne allergens: Pollen can be an allergen for some people, especially during its spring bloom.
Edibility: This plant is not typically eaten by humans.

How to identify it

Dark green, sticky leaves
Toothed leaf margins
Small, woody cones (strobiles)
Grayish-brown, fissured bark
Shrubby or tree-like growth habit

Height: 15 to 25m
Spread: 10 to 15m
Leaves: dark green, deciduous
Flowers: brown, reddish
Fruit: brown, Late summer to fall

Common problems

Aphids — Small, pear-shaped insects that feed on plant sap, causing distorted growth.
Alder leaf beetle — Larvae and adults feed on alder leaves, skeletonizing them.
Anthracnose — Fungal disease causing leaf spots and blight, especially in wet conditions.
Root rot — Fungal disease favored by waterlogged soils, leading to wilting and decline.

Growing it

Propagation: Seed, Cuttings
When to plant: Spring, Fall
Overwintering: As a hardy deciduous tree, Alnus glutinosa requires no special overwintering care in the ground. In containers, ensure the root ball is protected from extreme freezes by mulching heavily or moving the pot to a sheltered location.
In containers: Not well-suited for containers due to its large size and preference for moist, expansive soil conditions.

Seed Propagation

Collect mature 'cones' (strobiles) in fall or winter.
Extract seeds and stratify them by keeping them in moist stratification for 2-3 months at cold temperatures (around 34-41°F or 1-5°C).
Sow seeds in a well-draining, moist seed-starting mix in spring.
Keep the soil consistently moist and provide light shade.
Transplant seedlings once they are large enough to handle.

Cuttings

Take semi-hardwood cuttings in mid-summer.
Use a rooting hormone to improve success rates.
Insert cuttings into a moist, well-draining rooting medium.
Keep cuttings consistently moist and in a humid environment, such as under a mist system or in a propagator.
Transplant rooted cuttings once they have developed a good root system.

Plant alder in areas with consistently moist or wet soil, like near streams or in boggy spots, to ensure its best growth and ecological benefits.

Grows well with

Willow — Willows share similar wet habitat preferences and can help stabilize stream banks alongside alder.
Red Osier Dogwood — This shrub also thrives in moist conditions and adds visual interest with its colorful stems in winter.
Cattail — Cattails are excellent wetland indicators and provide habitat in shallow water areas where alder grows.
Marsh Marigold — This cheerful yellow wildflower blooms in spring in the damp soil around alder roots.

Keep away from

Waterlogging (extreme) — While it loves moisture, prolonged periods of stagnant, anoxic water can stress the roots.
Drought — Extended dry periods can significantly stress this moisture-loving tree.

Similar species

Green Alder — Green alder is a shrubby species typically found in drier, mountainous regions and has smooth, not sticky, buds.
Grey Alder — Grey alder prefers moist but not waterlogged soils and has greyish bark and leaves that are not sticky.

Science

Family: Betulaceae
Genus: Alnus
Order: Fagales
Class: Magnoliopsida
Native range: Europe, North Africa, and parts of Asia.
Conservation: Not of conservation concern.

It colonizes wet habitats, including riverbanks and bogs, and improves soil fertility through nitrogen fixation.

Value to wildlife: nectar source, larval host plant, provides nesting material
Pollinators: bees, moths
Uses: erosion control, windbreaks, wetland restoration, timber

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 3/9
Soil reaction: 5/9
Light: 7/9
Temperature: 6/9
Moisture: 8/9
Nutrients: 6/9

Taxonomy resolved against GBIF.

Questions people ask

What are the best conditions for Alnus glutinosa?: It thrives in moist to wet soils and full sun to partial shade.
How fast does it grow?: It's a relatively fast-growing tree, especially in ideal conditions.
Can it tolerate flooding?: Yes, it is very tolerant of waterlogged soils and periodic flooding.
When does it flower and produce seeds?: It flowers in early spring, and its cone-like fruits mature in the fall.

Where the name comes from

The scientific name 'Alnus' is the Latin name for alder. 'Glutinosa' comes from the Latin word 'glutinosus', meaning 'sticky' or 'glutinous', referring to the young shoots and buds.

Good to know

It's one of the few trees that can fix nitrogen from the air.
Its roots help stabilize soil in wet areas.
The wood is resistant to decay in water, making it useful for underwater structures.
It's often found growing in wet woodlands and along riverbanks.

Is your common alder looking unwell?

This page is a general guide. Pocket Botanist diagnoses problems from a photo of your actual plant, works out watering for your light and conditions, and reminds you when care is due.

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This guide was generated with AI and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.