Wetlands1 are defined by the presence of water – places where water covers the soil or where it is present at or near the surface for part of the year. That’s a wide-ranging definition, so it covers a wide range of wetland types and wetland habitats2!
Wetlands are special places when it comes to vegetation3. Many wetland species4 throughout Aotearoa5 New Zealand are endemic6 and range from the tiny swamp helmet orchid (Corybas carsei) that is only found in the Waikato’s Whangamarino Wetland to the tallest tree in Aotearoa – the kahikatea (white pine, Dacrycarpus dacrydioides).
Where particular plants live is determined by the amount of water that is present. Marshes and swamps usually have a gradient that moves from open water and saturated soils to drier upland soils. These are some zone characteristics:
- Aquatic – permanent open water that is usually more than 1 m deep. Plants like duckweed are submerged but with their flowering parts above water.
- Emergent – shallow water between 5 cm – 1 m deep. Plants like raupō (bulrush, Typha orientalis) or kuta (bamboo spike sedge, Eleocharis sphacelata) are partially submerged.
- Saturated – soils are saturated most of the year. Plants like harakeke7 (flax, Phormium tenax), tī kōuka (cabbage tree, Cordyline australis) and maire tawake (swamp maire, Syzygium maire) tolerate a mix of flooded and drier conditions8.
- Moist – soils are saturated at times but dry in summer. These conditions support trees such as kahikatea, mānuka9 (tea-tree, Leptospermum scoparium) and whekī (rough tree fern, Dicksonia squarrosa).
- Mesic – upland soils that may be saturated for short periods but are generally dry and mark the transition from wetland10 to other types of habitat11. These conditions support kōwhai (Sophora spp.), mamaku (black tree fern, Cyathea medullaris) and rimu (red pine, Dacrydium cupressinum).
Wetland plant adaptations
Wetland habitats present challenging conditions, so some plants have adaptations12 that help them survive. Wetland soils are saturated and become anaerobic – lacking in oxygen13. Plants need oxygen for respiration14. Rushes like wīwī, raupō and sedges like kuta have spongy tissues that form air channels inside of their stems. Known as aerenchyma, these channels move oxygen from the parts of the plant that are above water to the parts of the plant that are submerged. Pukatea (Laurelia novae-zelandiae) and swamp maire have special breathing roots called pneumatophores. These specialised roots stick out of the swampy soil and supply air to the submerged roots. Pukatea, swamp maire and kahikatea trees develop buttresses (flared trunks at the base of the tree) that support the trees in the swampy ground.
Many emergent wetland plants have elongated stems to ensure that a portion of the plant is above the water. This is important for both photosynthesis15 and reproduction.
Another challenging condition16 in some wetlands is access to nutrients17. Bogs are nutrient18 poor, so carnivorous plants like sundews (wahu, Drosera spp.) and bladderworts (Utricularia australis) gain additional nutrients by capturing insects and other invertebrates19.
Wetland (repo) plants and te ao Māori
Traditionally, repo were both grocery and hardware stores for Māori. Repo brimmed with food and sustenance20 (such as tuna21, kōura and various berries and seeds), materials for housing (such as roofing and insulation22) and plants for rongoā23 Māori to treat wounds and ailments.
Perhaps the one plant most symbolic of customary Māori life is harakeke. Harakeke is commonly found in wet areas throughout Aotearoa. Although it is no longer needed for creating the many items crucial for day-to-day living, harakeke still holds significant value in te ao Māori24. Raranga (weaving) tikanga25 and techniques are being revived and are flourishing. Harakeke heals both the people through rongoā and the whenua26 through riparian restoration.
Kuta is another wetland plant that is highly valued as a weaving resource. Woven gently, the kuta stem holds air, which provides warmth and softness in the finished product. These properties were valued in sleeping mats and as wall insulation for buildings.
There is significant mātauranga27 associated with the nurturing, harvesting and preparation of harakeke and kuta. Kōrero with local kaumātua28 and other whānau29 about these practices, especially when considering wetland restoration.
Related content
Explore our collection of rongoā Māori resources on the Science Learning Hub, including helpful notes for teachers. Log in to make this collection part of your private collection – just click on the copy icon. You can then add additional content, notes and make other changes.
Learn about the history of raupō from the time before people arrived in Aotearoa. Research shows this resilient, opportunistic plant – and taonga species30 – can play an important role restoring wetlands and freshwater quality.
Discover more about native31 plant adaptations in the article The uniqueness of New Zealand plants.
Useful links
These articles provide more in-depth about harakeke and kuta:
- Harakeke – weaving people together by Sue Scheele (Manaaki Whenua)
- Kuta – the giant of freshwater habitats by Mieke Kapa (Te Whare Wānanga o Waikato)
The Department of Conservation has information about wetland forests.
These sites have planting zone guides for particular regions:
Acknowledgements
Thank you to the editors and contributors of Te Reo o Te Repo – The Voice of the Wetland for permission and support to adapt this publication, and funding from Manaaki Whenua – Landcare Research and MBIE’s Unlocking Curious Minds initiative.
- wetland: An area of land that is saturated with water, often referred to as a swamp or bog. Wetlands may be seasonally or permanently water-logged with vegetation adapted for life under those soil conditions. Wetlands are known as repo in te reo Māori.
- habitat: The natural environment in which an organism lives.
- vegetation: Plant life.
- species: (Abbreviation sp. or spp.) A division used in the Linnean system of classification or taxonomy. A group of living organisms that can interbreed to produce viable offspring.
- Aotearoa: The Māori name for New Zealand, meaning Land of the Long White Cloud.
- endemic: Native to only one location. For example, species endemic to New Zealand naturally occur only in New Zealand but may have been introduced elsewhere in the world.
- harakeke: New Zealand flax (Phormium tenax).
- condition: An existing state or situation; a mode or state of being.
- mānuka: A shrub or small tree native to New Zealand, also know as tea tree (Leptospermum scoparium).
- wetland: An area of land that is saturated with water, often referred to as a swamp or bog. Wetlands may be seasonally or permanently water-logged with vegetation adapted for life under those soil conditions. Wetlands are known as repo in te reo Māori.
- habitat: The natural environment in which an organism lives.
- adaptation: A change in the structure or function of something. In biology, a change in a species, as a result of natural selection. Individuals with a particular feature (adaptation) are more likely to survive and reproduce than individuals without this feature.
- oxygen: A non-metal – symbol O, atomic number 8. Oxygen is a gas found in the air. It is needed for aerobic cellular respiration in cells.
- respiration: Can mean either cellular respiration (the process by which cells create energy) or gas exchange (breathing).
- photosynthesis: A process that uses the energy from sunlight to convert carbon dioxide and water into carbohydrates, releasing oxygen as a byproduct. Photosynthesis occurs in the green parts of plants, in algae and in some microorganisms.
- condition: An existing state or situation; a mode or state of being.
- nutrient: A substance that provides nourishment for growth or metabolism.
- nutrient: A substance that provides nourishment for growth or metabolism.
- invertebrates: An animal without a backbone, for example butterflies, worms, snails, insects, spiders and aquatic species such as crabs and jellyfish.
- sustenance: Nourishment and necessities for life.
- tuna: 1. A generic Māori word used to describe freshwater eels. There are numerous other specific names that relate to tribal origins and appearance. There are various species of eel, including the longfin eel, Anguilla dieffenbachii and shortfin eel, Anguilla australis. 2. A saltwater fish extensively fished commercially, genus Thunnus.
- insulation: Materials used to reduce the rate of heat transfer.
- rongoā: Traditional Māori medicine.
- te ao Māori: Māori world view (belief system), which provides a Māori epistemology (study of knowledge) of source, origin, knowledge, and application.
- tikanga: Māori customs and traditions that have been handed down from the ancestors.
- whenua: Land.
- mātauranga: Māori cultural knowledge and understanding of the world; Māori wisdom.
- kaumātua: Respected tribal elder(s).
- whānau: Extended family.
- taonga species: Species or biota that are of value to Māori or hold cultural significance to Māori, which may include introduced species.
- native: A species that lives naturally in a country, as opposed to species that have been introduced by the activity of humans.