Alnus

Part of speech: noun

Definitions

1. A taxonomic group of trees and shrubs referred to as alders, recognized for growing in wet habitats and possessing the unique trait of nitrogen fixation
2. A group of woody plants in the Betulaceae family, typically located near aquatic environments and distinguished by their unique reproductive structures and bark
3. A genus comprising species of trees and shrubs known for thriving in moist soils and capable of enriching the soil by fixing nitrogen

Etymology: The Latin "alnus" was the ordinary word for the alder tree, and the genus takes its name directly from it. English "alder" is a close relative, descending from Old English "alor" or "alr." The extra "d" in the English form is a later addition, similar to the one in "thunder," which comes from Old English "thunor." The tree's soil-enriching habit comes from its roots. Alders host Frankia bacteria in root nodules, which convert nitrogen from the air into a form the plant and surrounding soil can use. That is why alders often colonize poor or disturbed ground, and why they are planted to restore it.

Synonyms: alder