Alder
| Alder Temporal range:  | |
|---|---|
| Common alder (Alnus glutinosa) | |
| Scientific classification | |
| Kingdom: | Plantae | 
| Clade: | Tracheophytes | 
| Clade: | Angiosperms | 
| Clade: | Eudicots | 
| Clade: | Rosids | 
| Order: | Fagales | 
| Family: | Betulaceae | 
| Subfamily: | Betuloideae | 
| Genus: | Alnus Mill. | 
| Type species | |
| Alnus glutinosa (L.) Gaertn. | |
| Synonyms | |
| Genus synonyms 
 | |
Alders are trees of the genus Alnus in the birch family Betulaceae. The genus includes about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species extending into Central America, as well as the northern and southern Andes.