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Book cover - Common Weeds of New ZealandAn Illustrated Guide to
Common Weeds
of New Zealand


Lagarosiphon major


Reproduced from
Common Weeds of New Zealand
by Ian Popay, Paul Champion & Trevor James
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.

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Lagarosiphon major - lagarosiphonLagarosiphon major - lagarosiphon

Wholly submerged, vigorous freshwater perennial up to 4 m tall, growing from depths of up to 6 m. One of the oxygen weeds.

  • Flowers Pink, minute, 0.25 mm in diameter and up to 6 cm long, threadlike, singly in axils of upper leaves, female only in NZ. Flowers Jan.
  • Fruit Does not seed in NZ, reproduces vegetatively by stem fragments.
  • Leaves Alternate along the stem, but closely-spaced, overlapping and curled backwards. Dark green, up to 16 mm long by 2 mm wide. Crowded towards the tips of the stems, more spaced below.
  • Stems Fragile, slender, 3 mm thick, much-branched.
  • Roots Fibrous.


Clear, still or slow-moving, low fertility freshwater of ponds, lakes, streams and rivers.


Scattered throughout NI, more local in SI. Originally from South Africa.


The oxygen weeds include Egeria, Elodea and Lagarosiphon. In Lagarosiphon, the leaves are spirally arranged, not in whorls, and are 16 mm long, stiff and strongly recurved. The flowers are small, pink and float on the water surface. Lagarosiphon is similar to Elodea, but is stiffer and larger, with longer stems. Listed on the National Pest Plant Accord (see Introduction for details).

Derivation of botanical name

Lagarosiphon (Gr.) = thin tube, the narrow perianth tube; major (Lat.) = larger.


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Web-notes: Weed Links

On this site

Reproduced from Common Weeds of New Zealand:

External Links

WeedbustersWeedbusters New Zealand
Weedbusters is a weeds awareness and education programme that aims to protect New Zealand's environment from the increasing weed problem.
A free tool to assist farmers and agricultural professionals in decision-making regarding weed and pest identification, biology, impact and management.
Weed keyNew Zealand Weeds Key
An interactive identification key to the weeds of New Zealand. Developed at Landcare Research.

New Zealand Plant Conservation Network naturalised plants
Search for information on more than 2500 naturalised and weedy plants.
NZ Plant Protection SocietyNew 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."
Massey UniversityMassey 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.

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Last updated: March 1, 2021