General EcologyRead full entry
Heteranthera reniformis is a fugitive species of wetlands. Although H. reniformis can grow rapidly to form dense mats when competition is low, it is a poor competitor with sedges and rushes. It will grow well for a few years on the edges of ponds and marshes before it is shaded out (Horn 1994).
Phenology: Heteranthera reniformis is an annual even in the tropics (Horn 1994). The seedling is a rosette of leaves that grows in rich soil in shallow water. The rest of the plant reaches the surface where the procumbent stems can grow on mud or float on the water surface.
Blooming in North America mainly starts in July, but the plant can flower from late May to September and can continue until frost. In New York at the northern limit of its range, the plant is vegetative through June and July, flowers in August, and fruits in September (Young 1992). South of the equator in Paraguay, the species is in flower and fruit from August to May (Horn 1987b). The flowers are very ephemeral in nature; all flowers on an inflorescence will open in the morning and close by the afternoon of the same day. Flowers on submerged inflorescences will not open (Horn 1985, Horn 1994, Yatskievych 1994).
Germination: Seedbanks may exist in the soil for many years (Horn 1994). Conditions optimum for seed germination may include daily fluctuations in temperature. These fluctuations naturally raise and lower soluble oxygen levels and may act as a trigger for germination (Horn 1994).
Pollination: The flowers lack nectaries. Pollen collecting bees visit the conspicuous yellow anthers of the shorter stamens and pick up pollen from the pale blue or greenish anther of the long central stamen (Rosatti 1987 quoting from another publication: Lovell, The Flower and the Bee). The cleistogamously fertilized ovules develop into normal-sized fruits (Horn 1985).