🌿 Alder Tree
Alnus spp.
Tree
☀️ Sun
Full sun to partial shade
💧 Water
Moderate to high; naturally grows along streams; tolerates flooding
🗺️ Zones
3–7
📏 Spacing
15–25 ft
📐 Height
40–80 ft
🧪 Soil pH
5.5–6.5
⏱️ Maturity
Fast-growing; canopy in 10–20 years
Key:🤝 Grows well together❌ Keep apart☀️ Sun needs💧 Water🗺️ Hardiness zone
🤝 Companions (6)
🤝 Black Locust
Good companion — Alder Tree and Black Locust grow well together.
Good companion — Alder Tree and Sea Buckthorn grow well together.
Good companion — Alder Tree and Willow grow well together.
🤝 Native shrubs
Good companion — Alder Tree and Native shrubs grow well together.
Good companion — Alder Tree and Comfrey grow well together.
🤝 Clover
Good companion — Alder Tree and Clover grow well together.
⚠️ Keep Apart (2)
⚠️ Extremely dry soils
Keep apart — these plants do not grow well together.
⚠️ Competing tall plants in early years
Keep apart — these plants do not grow well together.
📝 Growing Notes
Alder trees are one of the most valuable nitrogen-fixing trees in temperate climates, increasing soil nitrogen by up to 200% through symbiosis with Frankia bacteria — making them a prized nurse tree in forest gardens. Research shows trees interplanted with alder grow 11–84% taller than those without. They are ideal pioneer trees for improving poor or disturbed soils.