Comparison of cold tolerance and seed propagation characteristics of three alien aquatic plants, Hydrocotyle spp.
This study was investigated cold tolerance and seed propagation characteristics to support proper control and management of invasive aquatic plants: Hydrocotyle ranunculoides, H. umbellata, and H. verticillata of Hydrocotyle spp. In winter, H. verticillata grew well under soil moisture conditions from wet to dry. The growth of H. umbellata has had adaptability widely with soil moisture condition from 30 cm submerged to a dry. The growth of H. ranunculoides was inhibited significantly under the dry up condition about 12% of volumetric water content in the soil under low temperatures. H. verticillata and H. umbellata produced no seeds. H. ranunculoides produced some seeds, of which approximately 60% were brown. Their seeds of H. ranunculoides have light dormancy, and their germination rate under the constant temperature condition of 15°C was higher than that under alternating temperature of 30°C/23°C or constant temperature of 30°C.