Alnus

Alnus 

(alder), a genus of monoecious or dioecious trees or shrubs of the family Betulaceae. The plants grow primarily in the northern hemisphere. There are between 42 and 47 species of alders, ten to 15 of which are found in the USSR. The leaves are alternate and serrate. Almost all species bloom in early spring, usually before the appearance of leaves. Alders are pollinated by the wind. The flowers are in catkins, and the fruit is a single-seeded, winged nutlet. In open areas, the plants begin bearing fruit after eight to ten years; in plantings, maturity is reached after 30 to 40 years. The trees and shrubs have a life-span of up to 100 or, rarely, 300 years. Propagation is by seed, stool shoots, and, in some species, root suckers. Rhizobia, or nodule bacteria, grow on the roots. Plants of the genus Alnus are found primarily along rivers and streams, in rich, well-aerated, and very moist soils. Some species are able to grow on rocky terrain or in damp sands.

The black alder (Alnus glutinosa), a tree measuring up to 30 m tall, has a graceful trunk and dark, fissured bark. Its glutinous leaves are dark green and obovate. It is found in Western Europe, Asia Minor, and northern Africa. In the USSR it grows in Western Siberia and in European Russia west of the line formed between Petrozavodsk and Perm’.

The European alder (A. incana) is up to 20 m tall. Its gray bark is smooth, and its light green leaves are acuminate, nonglutinous, and pilose. The tree is encountered in Western Europe and in the USSR—in the European part, Western Siberia, and the Caucasus. The European alder does not require as rich soil or as much moisture as do other species of Alnus. It gives off root suckers.

The species A. hirsuta has brown bark and large, pubescent leaves; A. japonica has ash gray bark and narrowly elliptic leaves. Both species grow in Japan, China, and the USSR—in Siberia and the Far East. A. fruticosa, a shrub or small tree reaching 6 m in height, has glossy, acuminate, ovate leaves. It is found in the Northeast European USSR, in the Urals, in northern regions of Western Siberia, and in Eastern Siberia.

Alder wood is light in color and has a reddish glow when exposed to the air. It is lightweight and can be used to make furniture, crates, and veneers. It is also used in the construction of underground and underwater structures. The bark of most species contains tannins. The tannin-rich cones of the black alder and the European alder are used medicinally in the preparation of tinctures and infusions. Such preparations are used as astringents for treating intestinal inflammations. Some species of Alnus are used in urban landscaping.

REFERENCES

Flora SSSR, vol. 5. Moscow-Leningrad, 1936.
Derev’ia i kustarniki SSSR, vol. 2. Moscow-Leningrad, 1951.

S. K. CHEREPANOV