Europe, Africa, India, SE Asia, Australia

General description

Submerged perennial <6.5m high. Green, occasionally red-streaked leaves in whorls 3-8; unlike Egeria or Elodea, has toothed edges. The mid ribs of the leaves are also toothed. Small inconspicuous flowers. Usually rooted in bottom, but can form floating mat.

Slow moving or static fresh water <12m deep: ponds, canals, streams. Tolerates low light, temps from 10-35ºC.

No seed produced in NZ. Spreads from tubers, turions, stolons, stem fragments by water, boats, fishing gear, machinery,

Dense mats block waterways impeding drainage, disrupting recreational activities, choking hydro turbines. Out-competes native species.

Site management

Nothing is very effective. Tubers, propagules and interference often makes the problem worse. Control should be undertaken by specialised agency.

Recommended approaches

1. Grass carp shows good potential.

Caution: when using any herbicide or pesticide PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.

Similar species

Egeria densa

Egeria lacks toothed leaf margins.

southern naiad
Najas guadalupensis

S naiad's leaves are on short branches.

Lagarosiphon major

Lagarosiphon has alternate leaves and lacks the toothed leaf margins.

Search tags

RPMS status

Surveillance - Whole Region
National Pest Plant Accord species - nationwide
Unwanted Organism - Whole Region
hydrilla - Main species image