Gray alder (Alnus incana)
Appearance: A shrub or smaller tree ranging in height from 3 do 15 m, sometimes even higher (do 20 meters). Wide or columnar crown, however, not vaulted high, only slightly sharpened.
The branches are very loosely placed, whorls or somewhat irregular, which makes the crown seem a bit scattered,
Smooth bark, dark gray-greenish, always slightly brighter towards the top, with many, vertically positioned lenticels. Stems silvery pubescent from below, on top – reddish brown. later naked and shiny. Buds on a stalk approx 2 mm, slightly bent to the side, purple, non-sticky. Torsion leaves, slightly spaced from one another and not overlapping. 2 front are sharpened strongly, oval or round in shape, about the length 7-10 cm, with clearly quilted edges, Top side matte, green, pants – gray-green and initially slightly hairy everywhere, and then with the hairs only on the veins of the lower leaf side. 7-12 pairs of larger nerves are placed exactly opposite each other or only slightly shifted, Foliage does not change color in late fall, staying green until it falls off.
Male cats are in groups of three or four, in the flowering season they have 5-8 cm in length. Female cats in larger groups, two to eight, when mature, they are woody cones approx 1 centimeter. Habitat: Gray alder likes loose gravely and sandy soils, rich in nutrients and periodically flooded,
Occurrence: Everywhere in central and northern Europe it is widespread and quite common in mountain riparian forests, along streams or small rivers, and also on permanently moist moraine loams. Less common in southern Europe; it is absent in the Mediterranean area,
Flowering period: March to April.
General thoughts: Gray alders are often planted to strengthen the soil on heaps or other fresh embankments. But they are also useful there for another reason. Alder roots coexist very closely with specific soil bacteria. They make up: for this purpose, as well as legumes, particular root tubers, colonized by filamentous bacteria. These microorganisms have a remarkable metabolic property: they can bind molecular nitrogen from the air and make it available to the root layer in the form of organic nitrogen compounds, For this reason, alder plantings on the initial soil enrich it with valuable nitrogen compounds and thus improve soil fertility.. For this reason, alders are considered to be very valuable pioneering tree species,
Gray alder differs from black alder by sitting female cats, without shafts, as well as more pairs of lateral nerves. A closely related green alder (Alnus) is a shrub tall to 4 m, with sessile, spicy donuts. It occurs in alpine thickets.