Alnus glutinosa

The tree Alnus glutinosa, native to most of Europe, including all of Britain.

The black alder thrives best in moist soils, and grows under favourable circumstances to a height of 20-30m, though often less. It is characterized by its short-stalked roundish leaves, becoming wedge-shaped at the base and with a slightly toothed margin. When young they are somewhat glutinous, whence the specific name, becoming later a dark olive green. As with other plants growing near water it keeps its leaves longer than do trees in drier situations, and the glossy green foliage lasting after other trees have put on the red or brown of autumn renders it valuable for landscape effect.

The stout cylindrical male catkins are pendulous, reddish in colour and 5-10cm long; the female are smaller, 2cm in length and reddish-brown in colour, suggesting young fir-cones. When the small winged seeds have been scattered the ripe, woody, blackish cones remain, often lasting through the winter. The alder is readily propagated by seeds, but throws up root-suckers abundantly.

It is important as coppice-wood on marshy ground. The wood is soft, white when first cut and turning to pale red; the knots are beautifully mottled. Under water the wood is very durable, and it is therefore used for piles. The supports of the Rialto at Venice, and many buildings at Amsterdam, are of alder-wood. Furniture is sometimes made from the wood, and it supplies excellent charcoal for gunpowder. The bark is astringent; it is used for tanning and dyeing.