Alnus serrulata aka Hazel Alder

Alnus serrulata belongs to the birch family, Betulaceae. Its names include hazel alder, smooth alder, and tag alder. It grows wild in eastern and central North America. Its range reaches from eastern Canada to Texas and northern Florida. It grows beside streams, ponds, and rivers, and in swamps. This deciduous shrub or small tree spreads through suckers. Several trunks and dense branches form patches of growth.

Garden plants reach 10–20 feet (3–6.1 m) tall. Their spread can reach 15 feet (4.57 m). RHS gives larger limits of about 26 feet (8 m). Growth is moderate, and the stems may twist. The bark stays smooth and gray to brownish gray. Small pores mark its surface. Young reddish-brown twigs have hairs and a three-sided pith. Green leaves grow in an alternate pattern along the stems. They have fine teeth, clear veins, and paler, hairy undersides. RHS notes that leaves fall green, without fall color.

Male and female flowers grow on the same plant. Both form catkins, but each has its own cluster. Male catkins look yellow-brown; the smaller female flowers look red. Missouri Botanical Garden places flowering in March and April. Its account places bloom before the leaves emerge. NC State also reports flowering later in spring. Female catkins become small, woody structures that look like cones. These hold nutlets and turn dark brown in fall. The cones stay on the branches through winter.

Grow this alder in sun or partial shade, not deep shade. It needs moist to wet ground and tolerates muddy soil. Clay and loam suit it, and poor soil need not limit growth. Root nodules fix nitrogen, which helps it grow with little fertility. Acid to neutral soil is a sound choice. High pH can cause chlorosis. Sources give USDA zones 4–9 and UK rating H5. RHS reports greater drought tolerance than in other alders. Damp sites remain its best garden setting.

Use it near ponds, in rain gardens, or along streambanks. Its wide root system helps hold soil against erosion. Birds and small mammals eat its nutlets and male catkins. Deer browse the leaves, sometimes causing heavy damage. It also supports harvester butterflies. Canker can cause major harm; mildew and leaf curl may occur. Other risks include Phytophthora, honey fungus, aphids, and leaf-mining insects. PFAF lists no known food use or hazard. Traditional uses include bark remedies and orange dye, not established food uses.