Red Alder

Alnus ruba 

leaves

  • Leaves:
    The leaves of the Red Alder are pinnately veined, doubly serrate and have revolute margins (see below). When comparing Red and White Alder leaves the Red Alder leaves are generally larger. However, it is important to note that these two species have hybritized to some extent in the Willamette Valley. Other differences between the two alders include the fact that Red Alder is both doubly serrate and has revolute margins while the While the only singly serrated and is not revolute. Alders are commonly found along streams and have associations with nitrogen fixing bacteria (see below).
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  • Revolute margins:
    This photo clearly shows how the edge of the leaf rolls under itself. Remember “R” for revolute for Red Alder!
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  • Cones:
    While most people associate cones with coniferous trees, Red Alder, which is not a coniferous species, has small woody cones.
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  • Pith:
    The pith of the red alder, when viewed in cross section is triangular.
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  • Root nodules:
    The alder’s association with nitrogen fixing bacteria form root nodules which provide a hospitable environment for nitrogen fixation.
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    Terms to Know 
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    Coniferous Species 
    Broadleaf Species