Hygrophila (
Hygrophila
polysperma
(Roxb.) T. Anderson) is
a plants which forms serious aquatic weed problems. Both
submerged and emergent growth forms occur. Nutritional
studies with a controlled release fertilizer and sediments collected
from hygrophila-infested areas were conducted with
the emergent growth habit to provide insights into growth of
this introduced plant. Plant dry weights for experimental 16-
week culture periods with low average temperatures were associated
with low amounts of hygrophila biomass as compared
to culture periods with high average temperatures.
Hygrophila cultured in sand rooting media with the controlled
release fertilizer produced as much as 20 times more
dry weight than plants cultured in sediments only. First-degree
linear regression statistics showed hygrophila dry
weights were highly related to ammonia nitrogen, magnesium,
sodium, and pH values in the sediments. These findings
show the close relationship of the emergent growth
habit of hygrophila to sediment nutrients. Analyses for certain
sediment characteristics may provide an indication of
the potential growth that may be expected for weed infestations
of this plant. Hygrophila grows year round in south
Florida; however, visual observations of canals and other bodies
of water indicate that lower amounts of hygrophila plants
occur during the cooler months of year than during the summer
season. These findings show the seasonal growth of
emergent hygrophila occurs with biomass dependent on
both sediment nutrients and temperature