Common alder
Alnus glutinosa · Betulaceae
📷 Willow · CC BY 2.5
The gardener's calendar
In autumn, ease off feeding and take the chance to clean up around common alder and prepare for winter.
ID card
- Common name
- Common alder
- Family
- Betulaceae
- Type
- Deciduous tree
- Adult height
- 18 to 20 meters
- Flowering
- March to April (catkins)
- Foliage
- Deciduous, dark green sticky
- Growth
- Rapid
- Hardiness
- Very hardy (down to -20°C)
- Origin
- Europe, Western Asia and North Africa
✓ Taxonomy verifiedSource: AI estimate · hardiness: reliability high.
Expert tips
The key tip
Black alder establishes quickly in wet or marshy soil. Water during the first year, then it'll manage on its own.
The common mistake
Installing it in dry or raised soil: it weakens and stays stunted.
The pro's trick
Plant it at the water's edge or in a damp zone: it quickly develops a vigorous shape there.
Care
Watering
Common alder thrives in humid environments and water-saturated soils. In temperate climates, regular watering is essential during the establishment of young plants. Once mature, watering during prolonged dry periods is sufficient. Young plants appreciate soil kept moist from May to September.
Light exposure
This tree prefers full sun or partial shade for optimal development. A sunny exposure promotes better branching and more generous flowering. It tolerates partial shade conditions very well, particularly along the edges of watercourses or water bodies.
Soil
Common alder adapts perfectly to humid, even marshy soils, where few other species would survive. It tolerates acidic, neutral and slightly alkaline soils. Soil rich in organic matter and well-drained at planting makes establishment easier, but compaction doesn't bother it.
Pruning and training
Pruning is generally not necessary: alder naturally develops a beautiful conical shape. Only remove dead, diseased or crossing branches. Intervene in late winter or after fruiting (October-November) to respect nesting birds.
Fertilizing
This tree is undemanding when it comes to fertilizer. A single application of well-decomposed compost at planting is sufficient. Alders naturally enrich the soil through their symbiotic association with nitrogen-fixing bacteria, making them very useful in agroforestry and ecological restoration.
Health and pests
Common alder is generally very resistant to diseases. Watch for the occasional appearance of scale insects or aphids during warm periods. In polluted aquatic environments, chlorosis may occur. Good air circulation and appropriate drainage prevent most fungal problems.
Did you know?
Common alder is one of the rare trees capable of fixing atmospheric nitrogen through symbiosis with actinobacteria housed in its roots, which traditionally made it the ideal plant for restoring exhausted land. In the Middle Ages and Classical period, its rot-resistant wood was precious for building foundation piles or underground pipes, notably in Venice where palaces rest on alder wood pilings.
Where to buy it
Best planted in autumn so the roots settle in before summer, or in early spring once the frost has passed. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, October, November.
Add this plant to my garden →Plants from the same family
- Silver birchBetula pendula
- Grey alderAlnus incana
- Dwarf birchBetula nana
- European Hop-hornbeamOstrya carpinifolia
- Turkish hazelCorylus colurna
- Italian AlderAlnus cordata
Tips generated and checked by Viridia — adapt them to your local climate.