Smooth Alder
Alnus serrulata
Last reviewed: October 2026
Smooth Alder is a multi-stemmed shrub that thrives in full sun and wet soil, often along streambanks and swamp edges, blooming with catkins from March through May.
Toxicity unknown
Smooth Alder (Alnus serrulata) is not listed by the ASPCA Animal Poison Control Center (opens in new tab) or the other sources we check, so we have no verdict for it either way. Absence from those lists is not a clearance. If your pet shows symptoms after eating any plant, call the ASPCA at (888) 426-4435.
The USDA PLANTS Database (opens in new tab) does not flag Smooth Alder as toxic to livestock.
Light
full sun
Water
high
Size
144"–240" H × 60"–120" W
Bloom
Mar, Apr, May
Native to
AL, AR, CT, DE and 25 more states
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Smooth Alder is a large native shrub that thrives in wet areas and grows 12-20 feet tall with a 5-10 foot spread. It produces catkins in spring and prefers consistently moist to wet soil conditions. This deciduous shrub works well for naturalizing wet spots or creating screening in areas with poor drainage.
Growing Smooth Alder
Grow Smooth Alder in full sun and high water. Mature plants reach 144 to 240 inches tall and spread 60 to 120 inches wide. Expect low maintenance to keep it looking intentional in a front yard.
How to care for Smooth Alder, by region
How to care for Smooth Alder where it is actually grown: year-round basics plus what to do each season, region by region, with the sources for each.
Care guidance last updated: October 2026
Eastern Corn Belt Plains (includes Columbus, OH)
Year-round
Hazel alder is a wet-soil shrub rated for USDA zones 4 to 9, and its listed native range reaches Ohio.
- It prefers moist to wet soil and is very flood tolerant.
- Full sun to part shade works.
- The wood is weak and breaks easily, so site it away from walkways.
- Canker can be severe and deer browse it heavily.
Fall
Fall is a good time to look for canker.
- Remove dead or cankered stems.
- Protect young plants from deer.
Removing dead stems keeps it neat if it is visible from the street.
Winter
Winter needs little care.
- Cage young plants against deer browse.
- Check for broken branches after ice or wind, since the wood is weak.
Spring
Spring brings early catkins in March and April.
- Birds and small mammals eat the pollen-rich male flowers.
- Check for stems broken over winter.
Summer
Summer is about keeping the soil wet.
- Water often if it is not in a boggy spot.
- Watch for aphids, leaf miners, and powdery mildew.
Sources: NC State Extension Plant Toolbox: Alnus serrulata, Lady Bird Johnson Wildflower Center: Alnus serrulata
In an HOA neighborhood
Smooth Alder takes more care to keep looking intentional in a front yard. Maintenance level: low. Consider it for backyard or mid-zone beds rather than the street edge.
Works well in: backyard only.
- Height exceeds typical HOA-friendly range
Wildlife value
The catkins provide early spring pollen for bees and other insects when few other plants are blooming. Birds use the dense branching for nesting and feed on the small nutlets produced later in the season.
Common questions
- When does Smooth Alder bloom?
- Smooth Alder produces catkins from March through May, typically before its leaves fully emerge.
- How much water does Smooth Alder need?
- This shrub prefers consistently moist to wet soil and is often found along streambanks, floodplains, and swamp margins. It does not handle dry conditions well.
- What light conditions does Smooth Alder prefer?
- Smooth Alder grows best in full sun but can tolerate some part shade, especially near water where soil stays consistently wet.
- Is Smooth Alder deciduous?
- Yes. Smooth Alder drops its leaves in fall and leafs out again each spring.
- Is Smooth Alder toxic to livestock?
- The USDA PLANTS Database does not flag Smooth Alder as toxic to livestock.
- Is Smooth Alder HOA-friendly?
- Smooth Alder takes more care to look intentional in a front yard. Consider it for backyard or mid-zone beds rather than the street edge.
These answers were drafted with an AI model from this plant's data. Verify care details with a local expert.
Native range data from vouchered herbarium specimen records and regional native plant society lists. Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.
If something looks wrong
Common plant problems, and what to check first
These come up on almost any plant. Each guide lists the likely causes in the order they are worth ruling out, with one thing to check before you act on any of them, and links to the source it came from.
- It is dying right after planting
- Leaves turning yellow
- Wilting even though I watered it
- Brown crispy leaf tips
- Bugs on the plant
Ready to grow Smooth Alder? Add it to your garden in Pollinator Patch to track it and get season-by-season care guidance.