Tree of the Week

Week 5 -  Alnus glutinosa; Alder

Alder is interesting in March because you can see the new male and female catkins held on the twigs alongside last year’s dried seed cases. These look a bit like pine cones and at this time of year are still clinging on to the tree in abundance. They are large enough to see clearly from the ground if you look up in to the canopy. The male catkins right now are about 4cm long and quite bright green and yellow because they are nearly ripe, though they’ll mostly be too high up to appreciate this. So, as long as you don’t confuse these catkins with Hazel (you won’t, this is a much bigger tree) or the seed cases with Plane (you won’t, these are smaller and oval not round) this is an easy one to spot! In summer the leaves are distinctive because they have a blunt or inward-curving end, rather than a common pointy-ended leaf shape, see below.

Alder is our most common waterside tree, a lover of all damp soils and a pioneer species. Their roots fix nitrogen in the soil, so when Alder woods are cleared the resulting ground is very fertile. They also help protect stream banks from erosion.