Salt marsh restoration practices based on the reintroduction of tides to hydrologically-altered wetlands may be hindered by a lack of specific knowledge regarding plant community response to environmental change. Since saltmarsh plant communities are controlled by physical stress tolerance and competition, we conducted a field experiment that measured effects of saltwater flooding and competitive interactions on plants as a guide for predicting habitat response to tidal restoration. Six plant species of New England salt marshes were studied: halophytes Spartina alterniflora, Spartina patens, and Juncus gerardii and brackish invasive species Phragmites australis, Typha angustifolia, and Lythrum salicaria. Plant shoots were transplanted across a gradient of three flooding and three salinity regimes and arranged into pair-wise competitive combinations. After one growing season, saltwater flooding was found to decrease transplant survival, biomass production, and/or relative growth for all species. Reduction in halophyte growth was largely due to increased flood duration; brackish species were most reduced by increased salinity. Interspecific competition also influenced species growth, although the short duration of the study may have weakened these effects. Transplants paired with S. alterniflora had reduced growth, but combinations with Juncus produced increased growth. Standardized factors of stress tolerance and relative competitive strength were derived for the six study species as a framework for understanding community-level changes in marshes. As an aid to resource managers, experimental results can be used to predict plant community response to existing and potential alterations in saltmarsh tidal hydrology.