|
 An
Illustrated Guide to
Common Weeds
of New Zealand
Alternanthera
philoxeroides
alligator
weed
Family
AMARANTHACEAE
Reproduced from
Common
Weeds of New Zealand
by Bruce Roy, Ian Popay, Paul Champion, Trevor James & Anis
Rahman
ISBN 0 473 09760 5
by kind permission of the
New
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. Appropriate acknowledgement
of the publication Common Weeds of New Zealand must always
be given.
Available from Manaaki-Whenua
Press and Touchwood
Books
Aquatic perennial,
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
the water.
- Roots Fibrous,
stems root from lower nodes.
Habitat
Warm, shallow, enriched,
fresh to slightly brackish water of drains, swamps, ponds, lagoons,
stream banks, dune hollows.
Distribution
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.
Comments
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).
Related
species
Nahui (Alternanthera
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.
Derivation
of botanical name
Alternanthera (Lat.)
= alternate anthers (the anthers are alternatively fertile and
sterile); philoxeroides (derivation unknown).
Web-notes:
Weed Links
On this site
Reproduced from Common Weeds
of New Zealand:
External Links
 Weedbusters
New Zealand
- Weedbusters is a weeds awareness and education programme that aims to
protect New Zealand's environment from the increasing weed problem.
 New
Zealand Plant Conservation Network Weeds Fact Sheets
- Search for 1500 weed fact sheets mainly derived from the Department of
Conservation's BIOWEB weeds database.
 New
Zealand Plant Protection Society
- Their main objective: "To pool and exchange information on the biology
of weeds, invertebrate and vertebrate pests, pathogens and beneficial organisms
and methods for modifying their effects."
-
 New
Zealand Landcare Trust
- Plant Pest information including Pictures, Distribution Maps, References,
Environmental Effects and Control.
-
- New
Zealand Aquatic Weeds
- Hosted by the weed management group of NIWA (National Institute of Water
and Atmospheric Research).
-
- Weed
Control Manual for the Bay of Plenty
- Weeds information compiled by Environment Bay of Plenty.
-
 Massey
University Weeds Database- A site providing information about New Zealand weeds and weed control.
It has a series of pages showing pictures of New Zealand weeds, notes on
identification and control. It also provides information on a university
paper entitled Controlling Weeds.
-
- Canterbury
Weed Guide
- A weed identification guide prepared by the Christchurch City Council.
-
- Australian
Plants as Weeds
- Part of the Association of Societies for Growing Australian Plants website.
- Department
of Agriculture Western Australia
- Collection of weed resources from the Department of Agriculture, Government
of Western Australia
- Weed
Society of Victoria
- Promoting wider awareness and interest in weeds and their management.
Includes a useful page of links
to other weed societies.
-
- Tamar
Valley Weeds Strategy
- Listing of common and botanical names, images, and information including
control methods for weeds found in Tasmania, and also on the Australian
mainland.
-
-
- New
Jersey Weed Gallery, USA
- Listing of common and botanical names and images, plus a small amount
of information for weeds that cause problems in the USA.
- Invasive
and Exotic Species of North America
- Images and other information from the University of Georgia.
- University
of California
- Weed Photo Gallery, with common and botanical names.
-
- World
of Weeds
- Weed-related resources including weed science, practical tools, gardening
tips about controlling weeds, and environmental news updates.
-
- Invasive
Species Specialist Group
- "The ISSG aims to reduce threats to natural ecosystems and the native
species they contain by increasing awareness of invasive alien species,
and of ways to prevent, control or eradicate them."
-
- Invasive
Woody Plants
- Collection of research and associated literature for invasive woody plants
in the tropics and the temperate zone.
-
- WeedScience.com
- Site that includes a comprehensive collection of weed images from around
the world.
-
-
 Books
on Weeds from FetchBook.Info
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