Generalities Black alder, Alder - Alnus glutinosa
There are about 15 Alder species, widespread in most of the temperate areas north of the equator, and on the mountainous areas of Central and South America. The species A. glutinosa is native to the European continent; it has light brown bark, quite rough, and dark green, rounded, medium-sized leaves, usually it does not reach dimensions greater than 20-25 meters. The crown is almost conical in shape, with fairly regular branches and fairly thin and not too vigorous branches. In early spring, before the leaves appear, it produces male and female catkins on the same tree, which in late summer and autumn leave room for the fruits, false woody pine cones of light green color, which in autumn release numerous seeds. Once dried, the fruits remain on the plant for many months, sometimes for years.
The alders are part of the Betulaceae family. To this belong other trees or bushes such as birches and kernels, all characterized by catkins: cluster inflorescences, hanging. They are spikes made up of flowers without petals or sepals. On each single catkin there are flowers of one sex, therefore only male or female. In alders, female ones have the characteristic of being particularly hard and woody. This helps us distinguish them from other plants in the same family. The seeds they release are winged. Pollination occurs by the wind and very rarely through insects. For this reason it is considered an essence that can cause allergy. The leaves are, in general, ovate, alternate and with a toothed margin.
The crown is oval, pyramidal, initially bright green and then darkening as the vegetative period progresses. It can take on a bush shape since, with appropriate pruning, several trunks can develop directly from the base. This type of treatment is carried out when you want to grow specimens to be used for carpentry or for the production of poles.
The name has an uncertain etymology. It could derive from the Celtic and mean "near the shore" or refer to the characteristic of the leaves to age prematurely.
Alders are medium-sized trees that can rarely reach 20-30 meters in height. They grow almost exclusively in wet and marshy areas or near waterways.
Female catkins give rise to cone-like fruits in which the seeds are found.