Effect of Substrate Composition and Fertility on Ramet Production in Crested Floatingheart (Nymphoides cristata)

Crested floatingheart is an introduced ornamental water garden plant that has escaped cultivation and invaded waters in the southeastern US. The species is particularly problematic in the canals of southern Florida and in the Santee Cooper reservoir in the Carolinas, where it has colonized more than 5,000 surface acres. Little is known about the reproductive potential of crested floatingheart, but it appears that most recruitment results from clusters of rhizomes that are colloquially referred to as “ramets”. In this study we investigated the effects of substrate composition and fertility on ramet production in crested floatingheart. Single plants were plugged into dishpans filled with one of five substrate mixes that were amended with one of four fertilizer rates and cultured under submersed conditions for 6 months. Analyses of variance 6 months after planting revealed that substrate composition had an early but weak effect on ramet production and that there was no interaction between the main effects of substrate composition and fertility level. However, there is strong evidence that fertility level drives ramet production by crested floatingheart. Ramet production was lowest in plants cultured with 0 g/L of fertilizer and highest in plants cultured with 4 g/L fertilizer. These results suggest that aquatic systems with high levels of sediment nutrients are most likely to experience severe infestations of crested floatingheart.