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Smooth Alder, Hazel Alder, Common Alder, Tag Alder, Black Alder
Alnus serrulata


Smooth alder is a small, largely thicket-forming tree to 40 feet tall found in open, sunny areas of the east Texas Pineywoods. It requires full sun, soils that are acid or at least neutral, and copious moisture, preferring to grow on edges of ponds, streams, swamps, and sloughs. The deciduous leaves are alternate, simple, and somewhat rounded. The flowers are borne in separate catkins. The male catkins are 4-inch-long cylinders, and the females produce aggregations of small nutlets that are 1/4 to 1/2 inch long.

Plant Habit or Use: small tree

Exposure: sun

Flower Color: yellow-brown or purplish catkins

Blooming Period: spring

Fruit Characteristics: aggregations of small 1/4 to 1/2 inch long nutlets

Height: to 40 ft.

Width: to 30 ft.

Plant Character: deciduous

Heat Tolerance: medium

Water Requirements: high water or bog

Soil Requirements: acid neutral

USDA Hardiness Zone: 5

Additional Comments: Alders are among the few nonleguminous plants that can fix atmospheric nitrogen via nitrogen-fixing bacteria in their root nodules.

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