Any of various deciduous shrubs or trees of the genus Alnus, native chiefly to northern temperate regions and having alternate, simple, toothed leaves and tiny fruits in woody, conelike catkins.

• 桤木一种桤木属的落叶灌木或乔木，原主要生长于北温带地区，有互生的锯齿形单叶，在其木本的锥体柔荑花序中有微小的果实