Curly waterweed

Curly waterweed (Lagarosiphon major) is a member of the Hydrocharitaceae family. It is a perennial submerged aquatic plant characterized by its dense, curled leaves and rapid growth rate. Originating from Southern Africa, it has become a globally recognized invasive species that disrupts aquatic ecosystems and human water use.

This plant thrives in stagnant or slow-moving waters such as lakes, ponds, canals, and reservoirs. In agricultural and rural settings, it poses a significant threat to irrigation infrastructure, drainage systems, and fishing waters, causing water flow blockages and interfering with the operation of pumps and hydro-agricultural machinery.

The biology of Lagarosiphon major is driven by fragmentation. The plant lacks sexual reproduction in many invasive ranges, relying entirely on vegetative growth. Small pieces of the brittle stem can detach and drift to new areas, where they easily root and form dense, oxygen-depleting mats that outcompete native aquatic flora.

The damage caused by this weed is severe. Beyond ecological degradation, it creates operational hazards for irrigation. By clogging intake screens and canals, it significantly increases maintenance costs for farmers and water managers. It also restricts recreational use and transport, making it one of the most problematic aquatic weeds in temperate climates.

Effective control requires a multi-faceted approach. Mechanical harvesting is common but carries the risk of spreading the weed further if not conducted with precision equipment that captures all plant debris. Chemical management involves the use of aquatic-approved herbicides such as diquat, applied during the active growing season, often combined with long-term habitat management to reduce light penetration.