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
forming dense floating mats on fresh or brackish water, and also
creeping onto wet dune hollows and cropping land near waterways.
Soft, hollow stems up to 2 m long. Opposite leaves 5-10 cm long.
White flowers similar to white clover, but smaller.
- Flowers White,
small papery florets in six- to twenty-flowered, clover-like heads
up to 13 mm in diameter. Flower heads solitary on stalks up to
9 cm long in leaf axils, or on short stalks at the ends of the
branches. Flowers Dec-Feb.
- Fruit Not
produced in NZ and reproduction is only from stem fragments.
- Leaves Waxy,
elliptical to egg-shaped, 5-10 cm long, margins entire, in opposite
pairs, stalkless or with a short leaf stalk. A ring of white hairs
is found between the bases of the opposite leaves.
- Stems Thick,
soft, hollow, grooved, reddish, branching, to 10 m or more long,
floating or creeping. Stem tips upright, as much as 1 m above
- Roots Fibrous,
stems root from lower nodes.
Warm, shallow, enriched,
fresh to slightly brackish water of drains, swamps, ponds, lagoons,
stream banks, dune hollows.
NI only. Abundant in
North Auckland waterways especially around Kaipara Harbour, Auckland
City, Waikato River mouth and one or two sites in Waikato and
Bay of Plenty. Originally from Brazil.
Likely to spread further
south as a serious weed of waterways and of nearby crops. Insects
introduced as biological control agents give good control in lakes,
but not on wet land. Listed on the National
Pest Plant Accord (see Introduction for details).
sessilis), native to NZ, is much smaller, with stalkless
axillary flower heads, occurring in damp open places, rarely in
dry waste areas and gardens, locally throughout NI, and in the
Lake Forsyth area in Canterbury.
of botanical name
= alternate anthers (the anthers are alternatively fertile and
sterile); philoxeroides (derivation unknown).