Common Name: Alder
Description: Deciduous trees or shrubs, monoecious.
Leaves alternate, petiolate, simple, pinnately veined; margins generally serrate, occasionally crenate or dentate.
Inflorescence a catkin, dichasial; dichasia each with 1 bract and 2 bracteoles. Male catkins pendulous; flowers 3 per dichasium; perianth usually lobed. Female catkins erect, shorter than male catkins, flowers 2 per dichasium; perianth absent.
Infructescence cone-like, ovoid or ellipsoidal; scales 5-lobed, thick, woody, persistent.
Distribution and occurrence: World: 41 species, Northern Hemisphere and South America (Andes). Australia: 2 species (naturalised), N.S.W., A.C.T., Tas.
Alders differ from birches (Betula) in that the female catkins are woody and do not disintegrate at maturity, opening to release the seeds in a similar manner to many conifer cones (ALA, accessed 14 Apr. 2023). Betula is naturalised in Vic. and (doubtfully) in A.C.T. and Tas., but is not recorded as naturalised in N.S.W.
Text by H.J. Hewson, adapted by Kerry Gibbons 18 Apr. 2023
Taxon concept: Flora of Australia [accessed 14 Apr. 2023]. Distribution and occurrence: Kew Plants of the World Online [accessed 6 Apr. 2023; APC [accessed 14 Apr. 2023].
| One species in NSW: Alnus glutinosa |
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