Modeling Accumulated Degree-Days for the Invasive Aquatic Plants Oxycaryum cubense and Eichhornia crassipes in Mississippi

Abstract Cuban bulrush [Oxycaryum cubense (Poepp. & Kunth) Lye] and water hyacinth [Eichhornia crassipes (Mart.) Solms] are floating aquatic plants that cause major ecological and economical harm in the southeastern U.S. They are commonly associated with each other due to the epiphytic nature of O. cubense, in that it utilizes E. crassipes (and other floating plants or objects) as a colonization substrate. Increasing global temperatures may allow for the northward expansion of both species in North America. The purpose of this study was to model plant growth (i.e., biomass) as a function of accumulated degree-days (calculated from air temperature) to predict peak biomass of both species growing in Lake Columbus, MS. According to the model, E. crassipes base temperature threshold at which growth does not occur was between 3 and 4°C, while O. cubense base threshold was − 3 to -5°C suggesting that O. cubense has a more prolonged growing season with the ability to grow during the winter, allowing it to continue growth and spread after other species have senesced. O. cubense’s low base temperature threshold suggests this species has the environmental tolerance to expand further north than was previously expected.