The World of Plants

a little database


General description: Monoecious tree closely related to the birches

Common name: Alder

Family: Betulaceae

Height: 25 – 30 m.

Aspect: sunny

Soil requirements: in general, alders thrive in very wet soil.

Why we use in horticulture:

Notes: Alder is particularly noted for its important symbiotic relationship with Frankia alni, a nitrogen-fixing bacterium. This bacterium is found in root nodules which may be as large as a human fist, with many small lobes and light brown in appearance. The bacterium absorbs nitrogen from the air and makes it available to the tree. Alder, in turn, provides the bacterium with carbon, which it produces through photosynthesis. As a result of this mutually-beneficial relationship, alder improves the fertility of the soils where it grows, and as a pioneer species, it helps provide additional nitrogen for the successional species which follow.


December 20, 2010 Posted by | Alnus, TREES (DECIDUOUS) | Leave a comment