Habitat

Hydrilla can grow in slow-moving or still freshwater bodies, as well as in slightly brackish water (<7 ppt salinity). It is tolerant of a wide variety of environmental conditions and competes well when conditions are limiting. Hydrilla can survive in low light, carbon, phosphorous and nitrogen conditions. It grows best between 20-27C but is hardy and can overwinter in freezing conditions through seeds and tubers.

Life Cycle

Hydrilla can reproduce both asexually and sexually, relying most heavily on asexual reproduction through tubers. Below ground, hydrilla grows small tubers to store nutrients. They rely on these tubers to overwinter, and to resprout in the Spring as temperatures warm. Hydrilla also produces turions (dormant buds) which detach from the plant in the fall. They spread downstream and lay dormant in the substrate until temperatures warm. The majority of hydrilla growth occurs in the late spring through early fall, when temperatures are between 20-27C. It grows rapidly, able to double its biomass several times throughout a growing season. It flowers in late summer and dies back as temperatures drop. When temperatures are freezing, hydrilla is reduced to overwintering in the form of tubers and turions in the substrate.

Ecological Threat

Hydrilla spreads rapidly and is able to outcompete native vegetation. It can grow in limited light and carbon conditions, allowing hydrilla to grow into dense mats that result in monocultures. In addition to impacting native plant populations, monocultures reduce habitat and food availability for animal species, leading to overall reduced biodiversity. Hydrilla monocultures also alter water chemistry and reduce oxygen levels, further endangering animal populations. Additionally, thick hydrilla mats have been known to clog mechanical equipment and hinder recreational activities.