Editing Alder (section)

== Description ==
[[File:LUT SEM Alder pollen 3kx.jpg|thumb|Pollen]]

With a few exceptions, alders are [[deciduous]], and the leaves are alternate, simple, and [[serration|serrated]]. The [[flower]]s are [[catkin]]s with elongate male catkins on the same plant as shorter female catkins, often before leaves appear; they are mainly [[wind-pollinated]], but also visited by bees to a small extent. These trees differ from the [[birch]]es (''Betula'', another genus in the family) 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 cone]]s.

The largest species are [[red alder]] (''A. rubra'') on the west coast of North America, and [[Alnus glutinosa|black alder]] (''A. glutinosa''), [[Native species|native]] to most of Europe and widely introduced elsewhere, both reaching over {{convert|30|m|ft|-1}}. By contrast, the widespread ''[[Alnus alnobetula]]'' (green alder) is rarely more than a {{convert|5|m|ft|abbr=on|adj=mid|-tall}} shrub.