General Description
A shrub swamp is an inland wetland dominated by tall shrubs that occurs along the shore of a lake or river; in a wet depression or valley not associated with lakes; or as a transition zone between a marsh, fen, or bog and a swamp or upland community. The substrate is usually mineral soil or muck. This is a very broadly defined type that includes several distinct communities and many intermediates. In northern New York many shrub swamps are dominated by alder (Alnus incana ssp. rugosa); these swamps are sometimes called alder thickets. A swamp dominated by red osier dogwood (Cornus sericea), silky dogwood (C. amomum), and willows (Salix spp.) may be called a shrub carr. Along the shores of some lakes and ponds there is a distinct zone dominated by waterwillows (Decodon verticillatus) and/or buttonbush (Cephalanthus occidentalis) which can sometimes fill a shallow basin. Birds that may be found in shrub swamps include both common species such as common yellowthroat (Geothlypis trichas) and swamp sparrow (Melospiza georgiana) and rare species such as the American bittern (Botaurus lentiginosus).

Characters Most Useful for Identification
Shrub swamps are very common and quite variable. They may be codominated by a mixture of species or be a near-monoculture of a single dominant shrub species. Characteristic shrubs include meadowsweet (Spiraea alba var. latifolia), steeplebush (Spiraea tomentosa), gray dogwood (Cornus racemosa), swamp azalea (Rhododendron viscosum), highbush blueberry (Vaccinium corymbosum), maleberry (Lyonia ligustrina), smooth alder (Alnus serrulata), spicebush (Lindera benzoin), willows (Salix bebbiana, S. discolor, S. lucida, S. petiolaris), wild raisin (Viburnum nudum var. cassinoides), and arrowwood (Viburnum dentatum var. lucidum).