The only British broadleaf to bear small woody cones, which stay on the twigs all winter beside next year's catkins
Alder.
Nature · Trees
Alder
Deciduous · to 28 m
Alnus glutinosa — Betulaceae
The tree of riverbanks, wet woodland and carr, the common or black alder is the only British broadleaf to carry small woody cones, which stay on the twigs all winter. It fixes nitrogen through bacteria in its root nodules, and its timber famously does not rot under water — the piles of Venice and Amsterdam stand on it.
How to know it
How to spot them
- ▸Small, hard, woody cones (strictly cone-like female catkins) persisting on the twigs through winter
- ▸Rounded leaves with a notched or blunt tip, never pointed, toothed and slightly sticky when young
- ▸Purple-brown buds on short stalks, held away from the twig
- ▸Growing with its feet in water: riverbanks, lake edges, wet woodland
- ▸Cut or bruised wood turns orange-red
How to know it
Rounded leaves with a notched or blunt tip — never drawn to a point — on purple buds held on short stalks
Alder.
Bacteria in its root nodules fix nitrogen, so it thrives on the poorest waterlogged ground
Alder. The symbiont is the actinobacterium Frankia alni.
Its timber does not rot while permanently wet, so it was driven as piles beneath Venice and Amsterdam
Alder. It also made clogs and the best charcoal for gunpowder.
Cut it and the pale wood bleeds orange-red, which gave rise to tales of a bleeding tree
Alder.
Phytophthora alni, a water-borne pathogen, has killed it along British rivers since the 1990s
Alder dieback.
The wetland woodland it dominates is known by the old East Anglian word carr
Alder carr.
Quick-fire facts
- •Alnus glutinosa — glutinosa means 'sticky', for the young buds and leaves
- •In the Betulaceae with birch and hornbeam; the only native British broadleaf with cone-like fruit
- •It fixes atmospheric nitrogen in root nodules through a symbiosis with the actinobacterium Frankia alni
- •Alder wood is durable under permanent water: it was used for piles in Venice and Amsterdam, and for lock gates and clogs
- •Alder charcoal was favoured for gunpowder
- •The wet woodland it forms is called alder carr
- •Alder dieback caused by Phytophthora alni has spread along British rivers since the early 1990s
- •The freshly cut wood turns orange-red, and the bark yielded a dye; Fender Stratocaster bodies are commonly alder
Drill it — 7 cards
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Sources
- Woodland Trust — Alder (Alnus glutinosa)