Alnus glutinosa - Native Alder - 60cm-100cm

Alnus glutinosa or Common Alder is a highly resilient broadleaf tree. As a native species across Ireland and Europe, it possesses an elite ability to transform waterlogged, poor, and unstable land into fertile, thriving environments.The dark green, glossy leaves have an unmistakable blunt, indented notch at the tip rather than a point.The greatest environmental strength of the Alder is its unique underground root chemistry, the tree's roots grow small bumps containing a very helpful bacterium which pulls nitrogen directly from the air, as its nitrogen-rich leaf litter decomposes, the alder serves as a natural fertilizer, making it a prime tool for reclaiming heavily degraded farmland, post-industrial sites, or nutrient-poor wetlands.

Key Features

• Form & Size: Broadly conical shape, growing rapidly to a height of 20–28 metres with a loose pyramidal canopy spread of 10–15 metres. 
• Foliage: Glossy green, rounded (obovate) leaves with a distinct indented or flat tip never pointed. Young twigs and emerging leaves are notably sticky to the touch.
• Flowers & Cones: Displays long, drooping yellow-brown male catkins alongside small, green oval female flowers from February to April. Over summer, the pollinated female flowers harden into woody, reddish-brown miniature pine-like cones that split open to release floating seeds and linger on the tree all winter. 
• Bark: Smooth and greyish green on younger trees, turning dark grey black and deeply fissured as it matures.

Growing Conditions

• Soil Preference: Heavily adapted to wet, heavy, clay, or boggy soils. It effortlessly tolerates waterlogged, poorly drained, and seasonally flood-prone areas where other trees succumb to root rot. It can grow in poor or compacted soils, though it avoids stagnant pools or highly acidic blanket bogs.
• Light: Best in full sun to light, partial shade.
• Hardiness: Highly wind-resistant, fully hardy against winter frosts, and moderately tolerant of maritime coastal salt spray.
• Soil Improvement: It acts as an environmental pioneer. Through root nodules containing symbiotic Frankia alni bacteria, it fixes atmospheric nitrogen into the ground, dramatically improving soil fertility for surrounding flora. 

Uses & Timber

• Water-Resistant Timber: Alder wood has the unique property of resisting decay underwater. Instead of rotting, it hardens and strengthens over time when fully submerged. Historically, it was used to build traditional Irish crannógs (lake dwellings), canal sluice gates, and famously acts as the underground foundation pilings for the city of Venice.
• Due to its split-resistant nature and easy workability, it was traditionally prized for carving clogs, wooden bowls, and furniture.
• Fuel & Foraging: Makes excellent charcoal (historically used for gunpowder) and is the traditional choice for smoking fish and meats. The bark and catkins were also gathered to create intense black or green natural dyes.
• Land Management: Extensively planted for riverbank stabilisation and flood prevention. Its highly dense, fibrous root systems knit loose waterside soil together to prevent erosion

Wildlife Value

• Avian Feast: The persistent winter cones serve as a vital natural bird feeder. Siskins, Goldfinches and Chaffinches congregate in winter flocks to extract the seeds.
• Invertebrate & Pollinator Host: Supports over 140 insect species. It is the primary food source for caterpillars and it's early-blooming catkins offer a crucial supply of nectar and pollen for emerging bees in late winter.
• Aquatic Ecosystems: Exposed root systems along river lines create sheltered, shaded underwater micro-habitats where otters nest and young trout or salmon hide from predators. Falling leaves decompose rapidly in the water, fueling aquatic food webs.