Alnus maritima or Seaside Alder is a deciduous shrub or small tree native to the Eastern U.S., with populations also found along the Blue River in Oklahoma. In nature, the tree will reach 20 feet (6m) tall. Leaves are glossy green above and light green underneath and are finely serrate. The elliptic leaves are 2.5-4 inches (6-10 cm) long and 1.5-2 inches (3-5 cm) wide with 8-10 pairs of lateral veins. Bark is smooth and gray in color. Trees in Oklahoma grow along stream banks in wet to moist soils. It has not been explained why the trees occur in Oklahoma since they are native to Eastern U.S. Our Botanists are trying to explain this. The trees are very easy to grow in containers and are hardy in the landscape in USDA zones 6 and 7.
Blooming: In the greenhouse and in nature, the trees bloom in the fall. Staminate catkins are up to 2.5 inches (6 cm) long. Pistillate catkins form near the leaf bases and are only 0.25 inches (6 mm) long. Cones are ovate to 0.5 inches (1 cm) long.
Culture: Alnus maritima needs full sun to partial shade with a moist to wet soil mix. In the greenhouse, we use a soil mix consisting of 2 parts peat moss to 2 parts loam to 1 part sand. The trees are kept moist at all times and we fertilize them monthly with a balanced fertilizer. Since they are native to stream banks, even during winter dormancy, period the plants are kept moist.
Propagation: Alnus maritima is very easy to grow from seed. Seed sown in spring readily germinates in 21-30 days from sowing.
Alnus maritima was featured as Plant of the Week June 12-18, 2009.
Guide to Past Plants-of-the-Week:
Cal's Plant of the Week was provided as a service by the University of Oklahoma Department of Microbiology & Plant Biology and specifically the late Cal Lemke, who used to be OU's botany greenhouse grower and an avid gardener at home as well. If the above links don't work, then try the overview site. You may also like to look at the thumbnail index. ©1998-2017 All rights reserved.