Many small shallow lakes and ponds in northern Minnesota are ringed by a band of speckled alder (Alnus incana ssp.rugosa).
Speckled alder can grow rather tall for a shrub, sometimes 20 feet or more. Each alder can produce several stems from its base, and when a number of alders occur together they can form a dense community called an alder shrub swamp.
Alders can be rather aggressive, and often don't leave room for other shrub species, but sometimes a few red-osier dogwoods (Cornus sericea (stolonifera)), native willows (such as Salix amygdaloides, Salix bebbiana, Salix discolor or Salix exiqua), or bog birch (Betula pumila) will be scattered here and there.
Alders are excellent at stabilizing the soil and they enrich the soil by adding nitrogen through their roots