Definition: In Scrub-Shrub Wetlands, woody plants less than 6 m (20 ft) tall are the dominant life form—i.e., the tallest life form with at least 30 percent areal coverage. The “shrub” life form actually includes true shrubs, young specimens of tree species that have not yet reached 6 m in height, and woody plants (including tree species) that are stunted because of adverse environmental conditions. All Water Regimes except Subtidal and Regularly Flooded-Tidal Fresh are included. Not all Water Regimes apply to all subclasses. 


Description: Scrub-Shrub Wetlands may represent a successional stage leading to Forested Wetland, or they may be relatively stable communities. They occur only in the Estuarine and Palustrine Systems, but are one of the most widespread Classes in the U.S. (Shaw and Fredine 1956). Scrub-Shrub Wetlands are known by many names, such as shrub swamp (Shaw and Fredine 1956), shrub carr (Curtis 1959), bog (Heinselman 1970), fen (Jeglum 1974), and pocosin (Kologiski 1977). For practical reasons we have also included stands of young trees less than 6 m tall. 


Subclasses and Dominance Types: 


  • Broad-leaved Deciduous -  In this Subclass, broad-leaved deciduous species have the greatest areal coverage within the shrub layer. In the Estuarine System, Dominance Types include species such as sea-myrtle (Baccharis halimifolia) and high-tide bush (Iva frutescens). In the Palustrine System, typical Dominance Types are alders (Alnus spp.), willows (Salix spp.), buttonbush (Cephalanthus occidentalis), red osier dogwood (Cornus stolonifera), honeycup (Zenobia pulverulenta), Douglas' meadowsweet (Spiraea douglasii), bog birch (Betula pumila), and young red maple (Acer rubrum). 


  • Needle-leaved Deciduous - In this Subclass, needle-leaved deciduous species have the greatest areal coverage within the shrub layer. Dominance Types include young or stunted tamarack and southern bald-cypress (Taxodium distichum). 


  • Broad-leaved Evergreen - In this Subclass, broad-leaved evergreen species have the greatest areal coverage within the shrub layer. In the Estuarine System, vast wetland acreages are dominated by mangroves (Rhizophora mangle, Languncularia racemosa, Conocarpus erectus, and Avicennia germinans). In the Palustrine System, the broadleaved evergreen species are typically found on organic soils. Northern representatives are labrador tea (Ledum groenlandicum), bog rosemary (Andromeda polifolia L.), bog laurel (Kalmia polifolia), and the semi-evergreen, leatherleaf (Chamaedaphne calyculata). In the South, shinyleaf (Lyonia lucida), coastal dogbobble (Leucothoe axillaris), inkberry (Ilex glabra), and the semi-evergreen, swamp titi (Cyrilla racemiflora), are characteristic broad-leaved evergreen species. 


  • Needle-leaved Evergreen - In this Subclass, needle-leaved evergreen species have the greatest areal coverage within the shrub layer. Examples of Dominance Types include young or stunted black spruce (Picea mariana) and pond pine (Pinus serotina). 


  • Dead - This Subclass includes stands of dead woody plants less than 6 m tall, regardless of their density, with less than 30 percent cover of living vegetation. If living vegetation equals or exceeds 30 percent in such stands, the Class and Subclass are based on the dominant life form of the living plants. Dead Scrub-Shrub Wetlands usually are produced by a prolonged rise in the water level resulting from impoundment by humans or beavers. In tidal areas, hurricanes, coastal subsidence, and sea level rise also may be responsible.

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