Illustrated Guide to
of New Zealand
Weeds of New Zealand
by Ian Popay, Paul Champion & Trevor James
ISBN 0 473 09760 5
by kind permission of the
Zealand Plant Protection Society
Publication or other use of images or descriptive
text on these pages is unauthorised unless written permission is
obtained from the authors and publisher.
of the publication Common Weeds of New Zealand must always
Available from Touchwood
bottom-rooted, vigorous, aquatic perennial. Occurs in fresh water
and can be up to 5 m tall in still water. One of the oxygen weeds,
denser than Elodea and Lagarosiphon.
- Flowers White,
conspicuously protruding just above surface, up to 20 mm in diameter.
Flowers have three petals 4-12 mm long and nine golden stamens.
Flowers occur in the axils of the upper leaves, two to three enclosed
in a spathe. Only male flowers are found in NZ.
- Fruit Fruits
not seen in NZ. Reproduction by regrowth from stem fragments.
- Leaves Very
dark green, up to 4 cm long, in whorls of four to six. Leaves
abruptly narrowed to a pointed tip.
- Stems Buoyant,
slender, brittle, 3 mm in diameter. Stems up to 1 m or more long,
much-branched, with nodes becoming closer together towards the
- Roots Bottom
Still, shallow, enriched
water in dams, ponds, drains, streams, rivers and lakes, in depths
of up to 5 m.
Abundant in Waikato
hydro lakes, scattered elsewhere in NI, and occasional, but spreading
in SI. Originally from South America.
Likely to spread to
new waterways. Listed on the National
Pest Plant Accord (see Introduction for details). The oxygen
weeds include Egeria, Elodea and Lagarosiphon.
In Egeria the leaves are dark green, in whorls of
four or five and 12-30 mm long. The flowers are white, conspicuous
and emerge above the water.
= after a Roman goddess of water; densa (Lat.) = dense.