Black alder
Alnus glutinosa
The nitrogen-fixer for wet feet — it thrives in soggy ground where most trees drown, feeds the soil and coppices hard for mulch. Go-to for stream edges and boggy corners.
Black alder in a syntropic line
Black alder belongs in the High layer as a Secondary nitrogen-fixing biomass species. Main production and shade trees for the line. Rough in-row spacing starts around 1.9 m in a syntropic row. Good line partners include Apple, Elder. As a Secondary species it carries mid-term yield and structure while climax trees slowly claim the canopy.
Tolerances and growing conditions
- Strata
- High
- Lifecycle
- Secondary
- Soil preference
- Clay, Loam
- Soil pH range
- 4.5 – 7.5
- Min. temperature
- -34°C
- Min. rainfall
- 800 mm/year
- Wind tolerance
- High
- Frost tolerance
- High
- Growth rate
- Fast
- Irrigation needed
- High
- Foliage
- Deciduous
- Waterlogging tolerance
- High
- Origin
- Europe
- Native to Portugal
- Yes
How to manage it
Excellent nitrogen-fixing biomass tree for wet zones, stream edges and poor soils; coppices vigorously and works well as a windbreak in riparian strips.
How to propagate
Sow seed in spring or take hardwood cuttings in winter; fast-growing nitrogen-fixer.
Guidance, not a guarantee — success varies by species and skill.
What to watch out for
Needs consistently moist to wet soil and struggles in prolonged drought. Actinorhizal N-fixer (fixes via Frankia, not rhizobia) — do not expect rhizobial-style nodulation.
Frequently asked questions about Black alder
Is black alder frost-hardy?
Yes for winter cold in many climates — generally hardy to around -34°C when dormant, with high frost tolerance in the catalog. Flowering crops can still lose a season to late frost, so site them carefully.
What soil does black alder need?
It does best on clay, loam ground, at pH about 4.5–7.5.
How much water does black alder need?
Plan for a rainfall floor around 800 mm/year, plus high irrigation once established.
Can black alder handle wet or waterlogged soil?
Yes — black alder has high waterlogging tolerance and copes with winter-wet ground.
What should I watch out for with black alder?
Needs consistently moist to wet soil and struggles in prolonged drought. Actinorhizal N-fixer (fixes via Frankia, not rhizobia) — do not expect rhizobial-style nodulation.
Black alder in soil templates
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