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  • Native to Africa and Southeast Asia

  • Forms dense surface mats that block sunlight and choke out native plants
Handful of Hydrilla

(Hydrilla verticillata)

Quick Identification

  • Plants grow 0.5 to 1 m tall

  • Leave grow in whorls of about five

  • Leaf edges are finely serrated

Hydrilla forms dense mats of vegetation that interfere with recreation and destroy fish and wildlife habitat.

Prevent the spread by practicing Clean Drain Dry for all water equipment. Report any sightings. Some herbicides are available but hand pulling only fragmenting the plants and roots spreading the invasion.

Flowers are tiny, white and semi-translucent with six petals. They grow on thread-like stems that branch from the top of the main stem.

Leaves & Stems
Leaves grow about five per whorl and are finely serrated. The mid-vein on the leaf can be reddish in colour. Stems grow up to 7 m and produce overwintering buds.

Hydrilla infestation

Tubers are 0.5 to 1 cm long and yellowish-white in colour.

Reproduction & Dispersal
Plants spread by stem fragments, buds, root fragments, and seed.


Seeds are produced by the tiny flowers that appear on the surface.

Preferred Habitat
Thrives in lakes, rivers, streams, ponds, and ditches.

Interesting Facts
Hydrilla is considered one of the worst invasive aquatic species.

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