Pingao at Mason Bay, Stewart Island.Sand dunes form part of the distinctive character of Southland’s coastlines. They work as a dynamic buffer between land and sea, being eroded and then built up again as part of natural physical processes. Sand-binding plants play an important role in the formation, development and maintenance of dunes. If dune plants are destroyed, eventually the dunes themselves can be lost. Find out more about Southland’s sand dunes and the special plants they contain.
About our dunes
Dunes play an important role in protecting the land behind them from the eroding wave action. The dunes themselves are constantly under threat from the eroding action of wind and waves. They rely on specialized sand-binding plants to hold them together.
The main sand-binding plant on Southland’s dunes was once the native pingao. These plants are well adapted to the dynamic conditions on the beach and send out runners which bind the sand. Pingao is a golden colour and was an important weaving material for Maori. However, today it is a threatened plant, and has to compete with introduced plants and survive grazing by rabbits.
Most of our dunes systems are now covered in marram grass. Marram was introduced in the late nineteenth century to stabilise sand dunes and reduce erosion. Unfortunately marram grass often outcompetes the native pingao. It impacts dunes by changing the way dunes build up, affecting their shape, and doesn’t provide suitable nesting habitat for some coastal birds.
Dune systems
Natural dune systems usually consist of three main zones:
- Fore dune – the front of the dune system, which takes the brunt of wind and wave action.
- Mid dune – of variable width, but usually makes up the main ‘body’ of the dune.
- Hind dune – the back of the dune system, which is usually more stable and is home to a greater range of plants.
In the mid dune area, you’ll often find dune hollows containing wetlands and pools. These are called dune slacks. Dune slacks form where the dune as been eroded to the level of the water table. You can often see pooled water in winter when the water table is high. Look for dune slacks at Oreti Beach and Waipapa Point. Dune slacks contain a range of generally small, creeping herbaceous plants and sedges. Some of the most common plants include selliera/remuremu, creeping eyebright, Nertera balfouriana, Mazus arenarius and Lilaeopsis ruthiana.
The hind dune system forms a transition between the exposed dune system and the more sheltered forest that would have originally backed the dune.
Dunes in Southland
Sadly, intact sand dune systems are now rare in New Zealand. Many of the dunes in Southland are dominated by the aggressive marram grass. Oreti Beach is our best known beach and sand dune system. It extends from Riverton to the mouth of the New River Estuary. You’ll find other sand dune systems at Waipapa Point, Omaui, Colac Bay and Wakapatu Bay.
However, you can still see a large, mostly intact dune system at ‘Three Sisters’, located in the Bluff-Omaui area. This dune system is on private land so you’ll need permission from the land owners before entering the property. Here you’ll see healthy populations of typical dune species, including a substantial cover of pingao.
Dune plant list
Use the following plants when replanting dune systems with natives:
Golden sand sedge / Pingao (Ficinia spiralis)
- Height: From 30cm to 70cm tall.
- Form: Grows in tufts, creeps across sand dunes, growing from rhizomes (underground stems).
- Leaves: Brilliant green and golden yellow or fiery orange blades, organized into tufts, stiff and curled, rough to touch, triangular in cross-section.
- Flowers: Small, white, arranged in spiral pattern at the tips of the leaves.
- Fruit: Dark brown spikelets.
Sand coprosma (Coprosma acerosa)
- Form: Low growing shrub forming a cushiony mass of interlacing branches.
- Leaves: Small, narrow.
- Flowers: Tiny, male and female flowers on separate plants.
- Fruit: Drupes, pale blue in autumn.
Sand tussock (Austrofestuca littoralis)
- Form: Yellow-green erect, loosely to densely tufted tussock.
- Leaves: Rolled, stiff, smooth, sharp-pointed.
- Flowers: Spikelets, large, clustered in a narrow head, like ryegrass.
- Fruit: Seedheads becoming brittle and breaking at maturity.
Shore spurge / milkweed (Euphorbia glauca)
Note: This is a nationally rare plant.
- Height: From 20cm to 40cm tall.
- Form: Erect, herbaceous, growing in open colonies from creeping rhizomes (underground stems).
- Leaves: Blue-green, fleshy.
- Flowers: Small, red-purple at end of long stems.
- Fruit: Seeds in three-cornered capsules.
Find out more
Find out more about Southland’s coasts in the following booklet:
- Coastcare – Caring for Southland’s coastal plant communities.
Booklets are available from the Invercargill City Council.