Hazel Alder

Alnus serrulata, commonly known as the Hazel Alder, is a deciduous shrub or small tree native to the eastern United States and parts of Canada. It typically grows in wetland areas, often found along stream banks, in swamps, and in floodplains. The growth habit of Hazel Alder can reach heights of 3 to 10 meters (10 to 33 feet), with a multi-stemmed form that can result in a bushy appearance. The branches are often crooked and may have a somewhat irregular shape, contributing to its distinctive look in the landscape.

The leaves of Alnus serrulata are alternate, simple, and ovate, measuring 5 to 10 centimeters (2 to 4 inches) in length, with serrated margins that give the species its specific epithet, “serrulata.” The upper surface of the leaves is dark green and glossy, while the underside is paler and may have a slightly hairy texture. The flowers are catkins that appear in early spring before the leaves emerge, with male catkins being elongated and pendulous, while female catkins are shorter and develop into small, woody cones that contain the seeds. These cones mature in the late summer and persist into winter, providing a food source for various wildlife. Hazel Alder plays a significant ecological role by fixing nitrogen in the soil, which enhances soil fertility and supports the growth of other plants in its vicinity. Additionally, it is used in streambank stabilization and erosion control due to its root system, which helps to anchor soil in place.

An interesting adaptation of Alnus serrulata is its ability to thrive in saturated soils, making it well-suited for wetland habitats. The species has a symbiotic relationship with nitrogen-fixing bacteria in its root nodules, allowing it to convert atmospheric nitrogen into a usable form for growth. This adaptation not only benefits the plant but also contributes to the health of the surrounding ecosystem by improving soil quality and supporting diverse plant communities. Hazel Alder is also valued for its wood, which is used in various applications, including furniture and crafts, and its bark has been utilized in traditional medicine by some Indigenous peoples.