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ALDER – Common name for the genus Alnus. A member of the Birch Family, it includes some 20 species and numerous varieties of hardy, deciduous trees and tall shrubs. Associated with cool, temperate climates, they grow mostly in cool, moist or even wet soils. They are all decorative plants with attractive stems, foliage and flowers. The staminate catkins blossom very early in the spring ; the pistillate catkins are woody, resembling small pine cones. In using alders we may take a lesson from nature in grouping plants suited to the same conditions. Intermingled with huckleberry, Cornus and sweet pepperbush, the Speckled Alder (A. tncana) lines pond margins and makes colorful copses in grass-grown wet meadows. Its dense root system retains the banks of swift streams and makes it a friend and ally in landscaping such places. Where logs are needed to build walks or retaining edges in wet soil, alder may be used as it will not decay easily when continually wet.

Two species, Alder incana and Alder maritima, will grow in wet soil ; both are bushy and may attain 25 ft. Others, which grow best in moist soil, are the native Green Alder (Alder crispa), a shrub to 10 ft. ; cordata, a round-headed tree to 50 ft. not hardy North ; rugosa, the Smooth Alder, a hardy tree to 25 ft. ; vulgaris, the Black Alder, an attractive tree to 70 ft., with many varieties showing interesting leaf forms, and japonica, a pyramidal form to 80 ft. conceded to be the most beautiful of all. In groups along the garden boundaries alders combine well with related trees such as birches, hornbeams and hazelnuts.

Propagation is by seeds gathered in the fall, kept dry and sowed in moist shady soil in the spring. The shrubby species grow from hard-wood cuttings and suckers, while the rarer varieties are grafted on potted seedlings indoors.