Egeria (oxygen weed)
|Botanical Name||Egeria densa|
IdentificationVigorous perennial grows submerged in up to 5m in water, forms a dense mat. Bottom rooting. Stems can be up to 5m long in still water, slender, brittle, much branched, buoyant. Soft linear leaves, dark grey-green, in whorls of 4 or 5 (sometimes 3-8), 10-30 mm long, abruptly narrowing to a sharp tip. Flowers to 20 mm across, 3 white petals, floating at water surface. Can be confused with Elodea and Lagarosiphon from which it differs by the denser, more leafy habit and 3-8 leaf whorls.
HabitatsNear the surface in the shallow and still waters of lakes. Still enriched water of ponds, drains, streams and rivers.
Impact to Biota and EcosystemsForms dense growths displacing natives and degrading natural character of rivers and lakes. A serious threat to dune lake species, some of which are threatened plants e.g. Hydatella inconspicua.
Dispersal Routes, Vectors, Infestation SourcesStem fragments root easily. Brittle stems break and are transported by machinery, boat trailers etc. No seed in NZ. Also introduced into water bodies through disposal of contents of fish ponds and tanks.
Cover weed mat to stop light access.
Diquat (Reglone) - see label rates. Within the Bay of Plenty region a consent is required from Environment Bay of Plenty before Diquat is applied to water.
This plant is prohibited from propagation, sale and distribution within New Zealand!