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Coastal Restoration
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This article was published in The Fringe, September 2013

The sand-binding plants that anchor our volatile sandy coastlines were once so under-rated that we imported marram grass (Ammophila arenaria) to replace them, organising work gangs of the unemployed to plant them on many of our beaches.  Even the most remote sand dunes on Stewart and Chatham Islands had extensive plantings to stabilise and protect land 'improvement' work from the wind-blown sand. Now we recognise the downside of all that marram grass we went to such lengths to import.

In 1978 Allan Esler analysed the critical difference in dune formation and found the native species built dunes up to 6 metres tall with the seaward slopes up to 16 degrees, whereas the exotic marram grass had higher, steeper dunes (8m tall and 25 degree slopes) which were much more prone to erosion by both wind and waves. Instead of helping stabilise our dunes, the marram grass had quite the opposite effect. It is interesting that in its natural area of distribution on the north Atlantic coasts of both Europe and America, it is tremendously effective, whereas on the Pacific coast of North America, it is considered a bad weed.

Today the two most prominent native sand-binding plants, Pingao and Spinifex, enjoy recognition of their attributes and they are now being widely cultivated for ecological restoration and to protect coastal habitats.

With experience and hindsight we now know the dynamics of sea, wind and sand have caused the evolution of these two native plant species into the most effective plants for dune protection and restoration. The job of these plants is to catch the sand as it is blown inland having being dumped on the beach by the ever-pounding waves that are attempting to erode the coastline and which must be repulsed if our shorelines are to be secure.

And so Pingao and Spinifex have adapted to provide the ideal combination of flexibility to withstand the winds and encroaching sea, and yet also be rigid enough to catch the flying sand, anchoring it and creating the protective dunes that line our beaches. The stout spreading rhizomes of both Pingao and Spinifex are designed to burrow under the sand, with roots at every node to securely hold each tuft of leaves. The leaves are tough, fibrous and elongated to sway in the winds and filter the wind-blown sand, actively encouraging their own burial from which they grow even more vigorously.

 

 

 

 

 

 

 

 

 

 

 

 

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