Studies were conducted in a wetland of the Mingo National Wildlife Refuge, southeast Missouri. Seed distribution pattern in the top 6 cm soil profile was examined. Soil temperature and water matric potential ((psi)) were monitored as various species emerged on the marsh surface during an artificial drawdown. Seeds of the four dominating species (Echinochloa crusgalli, Eleocharis obtusa, Polygonum hydropiperoides, and Xanthium pensylvanicum) were subjected to a wide range of diurnally fluctuating temperatures on a two-way thermogradient plate, and also to a selected range of (psi) in a greenhouse. Physical analyses of soil included an assessment of shear strength ((tau)) at various levels of (psi);Both quantitative and qualitative changes occurred in the seed bank during the study period. The seed distribution pattern, however, did not change significantly;Temperature regimes of 25-32/15-20(DEGREES)C favored seed germination in Echinochloa, whereas, a (psi) less than -76 kPa was found conducive for the emergence of this species in the field during a drawdown. A bimodal response to (psi) was discernible that may have some survival value. Maintaining soil water contents above the so-called field capacity should encourage a good stand of this species in the field. Seeds of Eleocharis germinated better in 25-29/14-19(DEGREES)C regime. Emergence in the field appeared little affected over a wide range of (psi). However, in the greenhouse, a (psi) below -33 kPa sharply reduced the rate of emergence in this species. Polygonum required a 19-21/8-9(DEGREES)C regime for better germination. Field and greenhouse study revealed the stress tolerance limit of this species to be -10 to -15 kPa (psi). Higher temperatures (27-33/16-20(DEGREES)C) as well as lower (psi) (-33 to -80 kPa) were found to favor germination/emergence of Xanthium;Results suggest that a slow drawdown with prolonged period of keeping the soil water content above the so-called field capacity will facilitate the establishment of a good vegetation cover of species useful to waterfowl.