Arbuscular mycorrhizal (AM) fungi are known to exist in wetlands, but little is known about their function in these environments. We conducted greenhouse experiments to study the effects of AM fungal assemblages collected from different vegetation types of a Florida wetland, under flooded and free drained conditions and at three P levels, on growth and nutrition of Typha latifolia and Panicum hemitomon. We also studied the effects of flooding on the spread of extraradical hyphae with P. hemitomon. For both plants no AM fungal assemblage had a consistent effect on plant growth and nutrition. For T. latifolia, flooding eliminated AM fungal colonization and, in the free-drained treatments, P amendment suppressed colonization. Furthermore, some mycorrhizal assemblages affected shoot- and root-P concentrations, but there were no significant plant growth responses. For P. hemitomon, the mycorrhizal association was suppressed, but not eliminated, by flooding and P amendment. Mycorrhizal colonization improved plant growth and P nutrition at lower P levels, but conferred no benefit or was detrimental at higher P levels. Extraradical hyphae were restricted by flooding, though variations among AM fungal assemblages were observed. We conclude that the impact of the mycorrhizal association on these wetland plants was a function of the complex interactions among the AM fungal assemblages, plant species, water condition, and P level.