Water Regimen and Depth Affect Hygrophila Growth and Establishment

Hygrophila (Hygrophila polysperma [Roxb.] T. Anders.) was grown in outdoor mesocosms to determine the effect of water regimen and water depth on hygrophila growth. Water regimen treatments included water that was stagnant, flushed twice per week, aerated, or continuously circulated. Hygrophila growth was highest when water was flushed twice per week; plants in this treatment produced the highest root and shoot biomass and had the longest and widest leaves. Water depth treatments included hygrophila submerged deep (54 cm), submerged shallow (27 cm), emerged, or sub-irrigated. Sub-irrigated plants produced higher root and shoot biomass than plants from all other treatments. These results indicate that hygrophila must become established as a terrestrial plant in saturated or near saturated soils; furthermore, after establishment in a terrestrial environment it can encroach into nearby water and grow as a submerged plant.