Common alder

Sun

Full sun to partial shade; best growth and shape in full sun.

Water

High; prefers consistently moist or wet ground and tolerates seasonal flooding. Poorly suited to dry gardens.

Soil

Moist to waterlogged clay, loam or sandy soil, preferably acidic to neutral. Tolerates compacted ground better than many trees.

Height

50-80 ft (15-24 m)

Spread

25-40 ft (7.5-12 m)

Flowers

Late winter to early spring, before the leaves open; hanging yellow-brown male catkins and small reddish female flowers.

Foliage

Rounded, toothed, dark green leaves, often with a notched tip; young leaves feel sticky. Usually falls green or dull yellow, with little autumn colour.

Growth

Fast, especially on moist ground.

Care needed

Low

• Cold hardy
• Wildlife

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   8 ft (2.3 m)

2. After 1 year

   12 ft (3.7 m)

3. After 2 years

   16 ft (5 m)

4. After 3 years

   21 ft (6.3 m)

5. After 5 years

   29 ft (8.9 m)

About 13 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the UK

Invasive in

the US, Canada and Australia

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Plant during the dormant season in moist ground, leaving room for a full-sized tree well away from drains and buildings.
• Water deeply during dry spells for the first two growing seasons; do not let the root ball dry out.
• Apply a 2-3 in (5-8 cm) layer of organic mulch, keeping it clear of the trunk.
• Do not routinely fertilise: root nodules containing Frankia bacteria help the tree obtain nitrogen.
• Stake only where needed on exposed sites, and remove support once the roots hold firmly.
• Outside its native range, check local invasive-plant advice before planting and remove unwanted seedlings promptly.

Pruning. Prune in late autumn or winter while dormant, removing dead, damaged or crossing branches and establishing a sound framework while the tree is young. Avoid topping or heavy pruning of mature trees; use a qualified arborist for large limbs.

Autumn

Plant after leaf fall where the soil is workable and not deeply flooded.

Winter

Prune young trees lightly and check ties and stakes.

Late winter

Leave catkins and woody fruits in place for seasonal interest and seed-eating birds.

Spring

Refresh mulch and inspect new leaves for beetle damage.

Summer

Water young trees during dry weather and check for thinning foliage or crown dieback.

Autumn

Pull unwanted seedlings while small, particularly beside ponds and streams.

• Use as a canopy tree at the damp edge of a large pond, with royal ferns and marsh marigolds beneath.
• Plant in loose groups on wet ground to create an informal woodland with winter catkins and woody fruits.
• Use in a broad shelterbelt where moist soil limits the choice of trees.
• Within its native range, include in streamside restoration or wildlife planting, allowing space for its mature roots and crown.

Garden styles it suits: Woodland, Wildlife garden, Bog garden, Rewilded, Winter interest and Grand estate.

Plant it with: Royal fern, Lady fern, Marsh marigold, Meadowsweet, Tufted hair grass and Siberian iris.

Wildlife: Catkins provide early pollen for insects, while seeds feed siskins, redpolls and other small birds. Leaves support numerous insects, and mature trees provide nesting cover. It is wind-pollinated, so its main value is not as a nectar plant.

• Phytophthora root and collar disease can cause small yellow leaves, crown dieback and dark bleeding patches on the lower trunk. Seek professional diagnosis, avoid moving affected soil or water, and use healthy nursery stock.
• Alder leaf beetles can leave leaves heavily perforated. Established trees often tolerate damage; inspect young trees and hand-pick beetles where practical.
• Drought causes wilting, leaf loss and poor growth. Water young trees deeply and choose a wetter site rather than relying on permanent irrigation.
• Wind damage and weak forks can develop in poorly formed trees. Train a sound framework when young and have damaged mature branches assessed by an arborist.

Not known to be toxic to people, cats, dogs or horses; no part is recognised as a significant poisoning hazard. It is not a food plant. Windborne pollen can cause substantial hay fever in sensitive people.

Where it spreads. Spreads by abundant seed, especially along waterways. It is considered invasive in parts of the northeastern and midwestern United States and southern Ontario, Canada, and is an environmental weed in parts of southeastern Australia, including Victoria and Tasmania. Check local restrictions before planting outside its native range.

• Grey alder (Alnus incana)

  Leaves usually have pointed rather than notched tips, with greyish, hairy undersides; young growth is not conspicuously sticky.

• Italian alder (Alnus cordata)

  Has glossy, heart-shaped leaves with clearly pointed tips, rather than the rounded, often notched leaves of common alder.

• Red alder (Alnus rubra)

  Has pointed leaves with strongly impressed veins and margins that curl slightly under; the undersides are paler than those of common alder.

Alnus is the Latin name for alder, while glutinosa means sticky, referring to the young leaves and shoots.

Propagation. Grow from seed collected from mature woody fruits in autumn. Sow outdoors in a moist seedbed or containers; spring sowing benefits from a period of cold, moist stratification. Keep seedlings consistently moist and transplant while small.

Accepted botanical name

Alnus glutinosa

In the US and Canada

Introduced in Canada and the lower 48 states.

Native range

Albania, Algeria, Austria, Baltic States, Belarus, Belgium, Bulgaria, Central European Rus, Corse, Czechoslovakia, Denmark and East European Russia.

Measured

Average height 1740 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.