In the “Pingao (or Pikao) the Golden Sand Sedge”
These Pikao (or pingao) is also known as the Golden Sand Sedge and its botanical name is Desmoschoenus spiralis1. It is endemic to (found only in) New Zealand's coastal environment and is one of our major sand binders along with Spinifex sericeus (spinifex or kowhangatara) and Austrofestuca littoralis (Sand Tussock or hinarepe), trapping sand to create dune systems2.
Pikao is a native perennial sedge2. Sedges are similar to grasses but can be distinguished from grasses by examining the stem/blades in cross section. Sedge blades are triangular in shape whereas grasses form a straight line.
Pikao resembles tussock in appearance. The foliage is coloured a brilliant green which turn a golden yellow or fiery orange at the ends. The leaves are organised into tufts and are stiff and curled and rough to touch. These characteristics help to minimise moisture loss in the harsh coastal environment and probably afford some protection from salt spray3,4. Pikao leaves turn a golden yellow when dried which is why Maori weavers prize them5.
Pikao are limited by moisture, and a lack of sand movement3. They are more tolerant to root salinity than marram grass6 and prefer exposed, unstable and bare sites2. Pikao's morphology is dependent on location, as its habit varies from north to south2.
Pikao reproduce in two ways, vegetative (rhizomes) (see photo) and sexually (seeds) (see photo)3,6. Rhizomes are long woody rope-like vegetative structures resembling roots that are sent out from the parent plants3. These contain nutrients, water stores and root initials that allow the rhizomes to establish into the sand and to send out leaves1. Rhizomes facilitate the dune building and stabiliation process by producing a large area of plant material and root systems to trap sand3. The extensive root systems produced as a result of vegetative reproduction also allows greater extraction of water from larger masses of sand3 which is essential for pikaos' survival. Vegetative reproduction is the main means of reproduction in pikao, enabling plants to survive indefinately4.
Seeds are produced sexually in the flowerheads6 (see photo). Pikao flowers are brown in colour and arranged in a spiral pattern (hence D. spiralis) on flowerheads that measure between 15-30cm in length2. These are sent up from the plant on long sturdy stems. Seeds then develop on the flowerheads in spikelets6 and mature between December and February, depending on location (maturity is reached later in more southern, cooler locations). Mature seeds are shiny, brown, egg-shaped and flat on one side however the exact shape depends on where the seed is located within the spikelet6. Seeds also vary in size with the largest being about the size of a match head2.
Learn more about seed collection and propagation.
Wind dispersal is the primary mechanism for dispersal over short distance, whereas transportation via seawater allows dispersal over longer distances3. Pikao seeds appear to have a dormancy mechanism which ensures seed viability over the longer-term3,6. Dormancy seems to set in shortly after seed maturity, after which germination may follow after the first year3. The length of time seed may remain viable for is unknown. A natural seedbank of unknown age exist at Island Park, Dunedin. There had been no existing plants in the area, but plants appeared following sand disturbance at a DCC sand mining operation7.
- Herbert, A. and Oliphant, J. (1991). Pingao: The Golden Sand Sedge. Nga Puna Waihanga, New Zealand.
- Bergin, D.O. and Herbert, J. W. (1998). Pingao on Coastal sand dunes. Guidelines for seed collection, propagation and establishment. CDVN Technical Bulletin No. 1. Forest Research Institute, Rotorua.
- DoC (1992). Pingao Recovery Plan. Otago Conservancy 1993-1998. Department of Conservation, Dunedin.
- Moore, L. B. and Adams, N. M. (1963). Plants of the New Zealand Coast. Paul's Arcade, Hamilton and Auckland.
- Sykes, M. T. and Wilson, J. B. (1989). The effects of salinity on the growth of some New Zealand sand dune species. Acta Botanica Neerlandica, 38(2), June.
- Courtney, S. P. (1983). Aspects of the ecology of Desmochoenus spiralis (A. Rich.) Hook. f. Unpublished MSc Thesis. University of Canterbury, New Zealand.
- P.pope, pers.comm. Reserves Officer, Dunedin City Council, Dunedin, New Zealand.