The Grey alder is very common between the Alps and the Urals. It is often planted as a pioneer plant in landfills, waste dumps and to fixing escarpment. The alder can fix nitrogen from the air and release into the ground again, which leads to the improvement of the soil.

It is a small to medium size tree 15–20 m (49–66 ft) tall with smooth grey bark even in old age, its life span being a maximum of 60 to 100 years.

The leaves are matte green, ovoid, 5–11 cm (2.0–4.3 in) long and 4–8 cm (1.6–3.1 in) broad. The flowers are catkins, appearing early in spring before the leaves emerge, the male catkins pendulous and 5–10 cm (2–4 in) long, the female catkins 1.5 cm (0.6 in) long and one cm broad when mature in late autumn.

The seeds are small, 1–2 mm (0.04–0.08 in) long, and light brown with a narrow encircling wing. The grey alder has a shallow root system, and is marked not only by vigorous production of stump suckers, but also by root suckers, especially in the northern parts of its range. The wood resembles that of the black alder, but is somewhat paler and of little economic value.

Although tolerant of a wide range of soils, the Grey Alder is especially good on dry, infertile soils where little else will grow. It does, however, need good light to do well.

Alder makes an attractive specimen tree and can be used for windbreaks, hedging and screening. It plays an important role in the reclamation of derelict land.

The catkins of Grey Alder are an early source of pollen for insects, and the ‘cones’ provide food for birds in winter. Its ability to grow well on the poorest of soils – even on spoil heaps – where the nitrogen-fixing nodules on its roots improve the fertility of the soil, makes it invaluable for reclaiming derelict land.

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Size

Ultimate height
Higher than 12 metres

Ultimate spread
wider than 8 metres

Time to ultimate height
20-50 years

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Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Fagales
Family: Betulaceae
Genus: Alnus
Subgenus: Alnus
Species: A. incana
Binomial name
Alnus incana

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