Hypericum fasciculatum and Stillingia aquatica are abundant codominant shrubs in South Florida depression ponds. Hypericum fasciculatum was studied from multiple perspectives: its competitive context, its adaptations to depression marsh seasonal extremes, and its reproductive biology. Hypericum fasciculatum showed slight intraspecific competition among mature individuals. Its seedling densities diminished with water depths. Interspecific competition with S. aquatica was not detected, probably due in part to markedly divergent root systems. Hypericum fasciculatum is more tolerant of competition from neighboring graminoids than is S. aquatica. The former has wide-spreading sinuous shallow main roots topped with short branch roots rising vertically into the overlying wet substrate. The leaves are dimorphic, with the mature foliage needlelike, having the stomates in abaxial slits. The inner bark is spongy, water-retentive, and substantially thicker than that of other measured local shrubs. Flowering is year-round with usually high fecundity, although flowers abort during drought stress. Seeds per fruit diminished in the wet vs. dry season and with insect-exclusion vs. open pollination. Flowering is protogynous, the buds opening before dawn with the stamens clumped at the base of the style. As the day progresses, the stamens become erect serially with the stigmatic pollen load increasing correspondingly, including with pollinators excluded. Evidence supports extensive self-pollination mixed with entomophily. Insect visitors are diverse.