The Urban Pantheist

Photos by cottonmanifesto. Speckled alders reach over the Muddy River in Brookline.

Urban species #361: Speckled alder Alnus incana rugosa

When a catastrophe happens to a habitat--a fire, a flood, or other vegetation-killing event--new plants quickly colonize the area. These plants tend to be those that spread on the wind or water, grow quickly, and like bright sunlight. Dandelions and ragweed are well-known annual weeds that fit this description, but even some trees and shrubs do as well. Speckled alder is one of these, growing in northern forests in the wake of forest fires, or where trees have been cleared for the construction of a new mall. It also likes to grow along streams and swamps, in rich wet soil. Its roots survive even if the top of the plant is cut or burnt away. It can spread vegetatively, the roots growing horizontally and sprouting new shoots. Like legumes, alders fix nitrogen in the soil, making growing conditions better for the plants that will eventually replace them.

Speckled alder is the eastern North American variety of gray alder, a species also found in Europe, and was previously considered to be a separate species. It can be an important food for mammals, including eastern cottontails and muskrats. Alders are distinctive for bearing both male and female flowers at the same time. The male flowers are catkins, similar to the flowers of the pussy willow, and the female ones developing into conelike fruit, like that of their relatives, the birch trees. The seeds are eaten by birds, including goldfinches and redpolls.


Persistent alder fruits hang in the air. Seeds not taken by birds will fall in the water and float to new habitats downstream.