Choose red alder for a large western wet site, white alder for a California stream, or smooth alder for an eastern thicket first.
Choose red alder, white alder, or an eastern thicket first
| Factor | Recommended | Avoid |
|---|---|---|
| Western large tree | Red alder — moist Pacific-coast ground; rolled leaf margins | Do not buy it as a 15-foot rain-garden shrub |
| California stream | White alder — interior and California banks; margins not rolled | Do not treat it as red alder on a coastal strip |
| Eastern thicket | Smooth alder — hazel alder for a stream or rain garden | Do not treat it as a hazelnut, and do not treat a common-alder tag as European black alder without checking the Latin |
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The first choice is size and range. Red alder is the large western tree. White alder is the California and interior stream tree, and you tell it from red alder by the flat leaf margin in summer. [1] [2] Smooth alder is the eastern thicket. If the tag only says alder, look at whether you have a 40-foot western tree or a 15-foot eastern shrub, then pick that kind. [3]
Which alder should I buy?
Buy red alder for a large western wet site, white alder for a California or interior stream, or smooth alder for an eastern thicket and rain garden.
How do I tell red alder from white alder?
In leaf, red alder has margins that roll under. White alder does not. In winter the twigs are hard to tell apart, so read the Latin on the tag.
Browse by kind
Match the western tree, the California stream tree, or the eastern thicket, then pick that kind. A smooth-alder thicket will not fill a Pacific-coast timber opening, and a red alder will not stay a 15-foot rain-garden shrub. Care for the plant you already have on How to Grow Alder.
Red alder
red alder is the large western tree, often sold as Oregon alder or western alder. Leaves have margins that roll under, and the inner bark turns rusty red when you nick it. Buy this group for a moist Pacific-coast opening, not for a 15-foot rain-garden shrub. It is Alnus rubra.
White alder
white alder is the California and interior stream tree. It takes heat and wind if the soil stays wet. Leaf margins are not rolled under, which is the usual summer way to tell it from red alder. It is Alnus rhombifolia, not a small eastern thicket.
Eastern thicket
smooth alder is the eastern suckering shrub or small tree, also called hazel alder, tag alder, or brookside alder. It holds a stream bank or rain garden at about 10 to 20 feet. Tags may say common alder or black alder; in the East that is still this species, not European black alder. [4]
If you want a 15-foot rain-garden thicket, buy smooth alder — red alder is a large western tree.
FAQ
Is common alder the same as European black alder?
Often no. In the East, common alder and black alder on a native tag are usually smooth alder, Alnus serrulata. European black alder is Alnus glutinosa, a different species that is not in this catalog.
Is speckled alder in this catalog?
No. Speckled alder is Alnus incana, and Sitka alder is another western shrub. The three kinds here are red alder, white alder, and smooth alder.
Is hazel alder a hazelnut?
No. Hazel alder is smooth alder, Alnus serrulata. Hazelnut is Corylus. See How to Grow Hazelnut if that is the tag you have.
Related guides
References
- [1] NC State Extension Gardener -
https://plants.ces.ncsu.edu/plants/alnus-rubra/ - [2] Oregon State University Landscape Plants -
https://landscapeplants.oregonstate.edu/plants/alnus-rhombifolia - [3] NC State Extension Gardener -
https://plants.ces.ncsu.edu/plants/alnus-serrulata/ - [4] Lady Bird Johnson Wildflower Center -
https://www.wildflower.org/plants/result.php?id_plant=ALSE2
This note is part of Alnus Guides.
More type comparisons by plant are gathered in Types of Plants Guides.
Updated: Reviewed by Bosquelle Editors