Aquatic plants

Isolepis fluitans subsp. fluitans. Photographer: Jeremy Rolfe.

Freshwater aquatic plants (also called macrophytes or hydrophytes) are those that have adapted to living in or on aquatic environments. Aquatic plants are an ecological rather than a taxonomic group and include obligate and facultative (or amphibious) species, representing a range of life forms; submerged, free-floating, floating-leaved, erect emergent and sprawling emergent. Aquatic plants are considered distinct from marine algae or seaweeds.

Unlike New Zealand's terrestrial flora, 66% of our indigenous freshwater flora are common with Australia (Champion and Clayton 2000). In a similar way Chatham (Rekohu) Island has a subset of the New Zealand freshwater flora, with 32% of New Zealand macrophytes present (Champion and Clayton 2004). These natural introductions are presumably the result of seed transfer by migratory waterfowl or wind dispersal.

Potamogeton suboblongus (mud pondweed, left) and Myriophyllum propinquum (common water milfoil, right). Photos by Jeremy Rolfe.

There is a diverse range of taxonomic groups comprising aquatic plants including; charophytes (specialised algae resembling higher plants with 

1 family, 4 genera, 18 species), fern allies (1 family, 1 genus, 2 species), ferns (2 families, 3 genera, 4 species), proto angiosperms (3 families, 4 genera, 5 species), monocotyledons (14 families, 24 genera, 35 species) and dicotyledons (15 families, 26 genera, 53 species). Thus a wide range of taxonomically unrelated species have colonised aquatic habitats, often with only one or a few species representing an individual family which has a much greater number of terrestrial representatives. The largest genera are Nitella (11 indigenous, including at least 3 endemic species), Myriophyllum (6 indigenous including 3 endemic, 1 alien species), Potamogeton (4 indigenous including 2 endemic, 2 alien species) Chara (4 indigenous including 1 probable endemic, 1 alien species), and Ranunculus (4 indigenous including 2 endemic, 1 alien species).

For more information see*

  • Champion, P.D.; Clayton, J.S. (2000). Border Control for potential aquatic weeds. Stage 1. Weed risk model. Science for Conservation 141.
  • Champion, P.D.; Clayton, J.S. (2004). Aquatic vegetation of Chatham Island (Rekohu). DOC Science Internal Series 164.
  • Coffey, B.T.; Clayton, J.S. (1988). New Zealand Water Plants: A guide to plants found in New Zealand freshwaters. Ruakura Agriculture Centre, Hamilton.
  • Johnson, P.N.; Brooke, P.A. (1998). Wetland plants in New Zealand. Manaaki Whenua Press, Lincoln.
  • Free aquatic plant information from NIWA (National Institute of water and Atmospheric Research)

*The Network is not responsible for the content of external internet sites

Trithuria inconspicua. Photo by Jeremy Rolfe.

This page last updated on 25 Sep 2012