Common Alder (Alnus glutinosa) Growing & Care Guide for Gardeners
Article by Dean Ravenscroft, Ph.D. - Updated 31st Jan 2024
- Plant Characteristics: Alnus glutinosa is a medium-sized, deciduous tree known for its rounded habit and glossy, dark green leaves. It produces catkins in early spring and has the unique ability to improve soil fertility by fixing nitrogen.
- Growing & Care: Thrives in wet, poorly drained soil and can tolerate a wide range of pH levels. It's particularly suitable for riverbanks and wetland areas. Requires minimal care once established, but may benefit from occasional pruning.
- Tips for New Gardeners: An ideal choice for gardeners looking to plant in damp or wet conditions. Its ability to improve soil quality makes it a valuable addition. Be aware of its size and spread when choosing a planting location.
Alnus glutinosa, commonly known as the Common Alder, European Alder, or Black Alder is in the same family as the birch: the Betulaceae family.
This low maintenance tree can grow pretty fast, is hardy in US zones 3-7 (UK H7), and has the potential to reach 60 feet (18 m) high in full sun or partial shade (typically reaches around 40 feet (12 m)).
The Common Alder tree has an upright nature and the canopy can spread out to about 13 to 26 feet (4 to 8 m).
Expect a Common Alder tree to reach its full size in about 20 years in the right conditions – taking up to 50 years in unideal environments.
Alnus glutinosa - Black Alder on a creek line photograph by Oor Woolie.
Suitable locations include use for hedges, rain gardens, and windbreaks. Alnus glutinosa is quick to establish in poorer soils, making it useful for reclamation schemes in areas with wet soils.
If grown on river banks, these deciduous trees can help stabilize the soil.
Its wood is useful for underwater building and smoking fish and coffee.
Black alder can grow in many kinds of soil, such as medium loamy to heavy clay. It can successfully tolerate maritime conditions. It can also grow in nutritionally poor soil but prefers a pH level above 6.
The flowers of Common Alder can be both male and female on the same tree (monoeclous). The winter male catkins and woody cones are ornamental and make the Alder easy to identify.
Bees use the pollen from catkins, and birds and small animals feed on the seeds during the winter. Fish also benefit from free food if the trees grow on riverbanks.
Gardener's HQ Guide to Growing Common Alder
The propagation of black alder is very simple.
Seed grown in flats during winter will germinate in the spring if lightly covered with soil.
The young plants can be pricked out and planted in pots to be planted out in permanent locations in summer.
Plants can also be started in spring but should not be covered. They should be left to grow throughout the year and planted the following summer.
Plants can also be propagated from hardwood cuttings taken during dormancy, once leaves have fallen or before new buds have begun to form.
Watch out for pests such as sawflies. Alder sucker (Psylla alni) is commonly seen but rarely causes any issues.
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Alnus glutinosa Growing and Care Guide
- Scientific Name: Alnus glutinosa.
- Common Name: Common Alder, European Alder, European Black Alder.
- Growing Zone: USA: 3 to 7; UK Hardiness Zone H7 (considered hardy to temperatures lower than -20°C / -4°F).
- Life Cycle / Plant Type: Tree.
Plant Details
- Plant Height (Inches): 300 to 600.
- Plant Spread (Inches): 300 to 420.
- Time of Bloom: Spring.
- Flower Details: Purple, Red.
- Leaf Foliage: Green.
- Fruit:
- Growth Form: Oval, Pyramidal.
Ideal Growing Conditions
- Best Light Conditions: Partially shady to full sunlight.
- Rate of Growth: Average pace.
- Suitable Soil Types: Acidic, Alkaline, Clay, Loamy, Neutral, Sandy, Slightly alkaline, Well drained.
- Soil Moisture: Moist/Wet.
Caring Conditions
- Care:
- Level of Maintenance: Low.
- Propagation: Seed or hard wood cuttings.
- How to Prune: Requires little to no pruning. In some cases hard pruning can be disruptive.
- Pests: Can get alder sucker and leaf-mining sawflies.
- Diseases: Susceptible to Phytophthora.
Further Information
- Can Attract:
- Tolerant of: Drought, Clay Soil, Wet Soil, Air Pollution.
- Best Garden Use: Firewood, Areas requiring pest tolerance, Pollard, Screen.
- Family: Betulaceae.
- Closely Related Species: Betula, Carpinus.
- Miscellaneous: Non-native to North America, Naturalizing, Wetlands plant, Inconspicuous flowers or blooms.
- Genus Detail: Alnus.
- Further Reading and References: Here and Here.
I hope that you enjoyed this guide on how to grow Alnus glutinosa. You may also enjoy the following Gardener's HQ growing guides for plants great to use in screening areas : How to grow Datura and Geum plants.
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