Botanical sheet dedicated to the black alder, Alnus glutinosa
The black alder: a species for river banks
The glutinous alder, Alnus glutinosa, is a deciduous tree which fixes the banks, cleans up and enriches spongy soils and captures nitrogen (thanks to nodosities present on the roots) for its own benefit; it is therefore the typical tree of the banks of watercourses and marshy areas. Very common in France (except in the Mediterranean region), it is a very popular subject in eastern France. It is a species that requires light and has difficulty with competition from other trees: it needs a large living space.
Description of the black alder
The alder, sometimes called alder or worm, has a deciduous foliage with a rather dense cover. Its top is conical, its branches erect (almost horizontal), and its male flowers (long hanging catkins) and female flowers (short erect catkins) are borne by the same individual. The pollination is done by the wind.
The bloom, during March, is discreet and precedes the exit of the leaves. The fruiting composed of small cones (the strobiles) is regular and abundant.
Of very fast growth; the black alder has a longevity comparable to that of the man; it lives between 60 and 80 years.
The enemies of the black alder
Microscopic fungi carried by the waterways cause root rot, the outcome of which is fatal.
The black alder is also sensitive to deer rubbing (marks that deer make on the trunks by rubbing their antlers).
The qualities of the black alder
The black alder is not afraid of water; it is rot-proof and has often been used for the construction of foundations, water pipes or pilings. The city of Venice is built on alder piles.
The wood of the black alder is orange in color. It is light and soft, easy to work. It is very often used in turning and furniture.
Growing tips
Alder should preferably be planted in deep soil, along waterways. It has a high water requirement and tolerates well asphyxiation by flooding.
It tolerates soils with a pH ranging from neutral to very acid.
Demanding in light, its fast growth compensates for its weak longevity.
