Strand vegetation

November 19, 2019

Although ‘strand vegetation’ is an established ecological term for plant communities that inhabit coastal margins, the title of this journal entry refers more to the bizarre ‘rafts’ of wiry strands on which islands of flowering exotic weeds grow at Rarangi Beach.

The flattened nests of filamentous, metallic stems on which these ad hoc wildflower gardens form belong to the leafless pohuehue (Muehlenbeckia ephedroides, shown below) – an aberrant misfit that has decided that leaves aren’t entirely helpful to the challenging circumstances of its existence. Another look at the image above reveals that this garden (like the surrounding islands of vegetation) has established in a patch of shingle that has been consolidated by M. ephedroides.

In contrast to the ‘volunteers’ that have jumped on top of the slightly more favourable conditions provided by leafless pohuehue (whether because of the accumulation of humus or increased moisture preservation), spur valerian clung to the margins of low mounds of the distinctive prostrate matagouri (pictured below, left) that is found here and in other exposed coastal habitats (such as at Nelson’s Boulder Bank).

Growing even closer to the waterline, native spinach (Tetragonia tetragonioides; pictured above, right) was generally free from the attentions of the kinds of weedy wildflowers growing so enthusiastically at a marginally greater distance from the shore. Other than being fairly typical of spots where one normally encounters native spinach, its position right out in the midst of the shingle beach also exemplifies the place in which edible coastal herbs often develop their best flavour (due to nature’s liberal applications of salt).

In an adjoining cove, I was pleasantly surprised to see a particularly good specimen of Melicytus orarius (formerly part of the Melicytus obovatus complex) growing on a rocky outcrop, not far from its close relative, Melicytus crassifolius. I had seen this species growing at multiple points around Wellington’s coastline, as well as Melicytus obovatus in the Nelson region, but had never come across it within Marlborough.

The final mention goes to a species whose presence at Rarangi is of particular significance. Sand tussock (Poa billardierei, pictured below) is increasingly rare in many parts of the country, and is also of significance as an attractive species for use in dune restoration (due to its golden-brown colour and wheat-like flowerheads).

This species, also known by the more lyrical name of hinarepe, is often found in association with a species of native sand daphne (Pimelea urvilleana). The latter is a sprawling, white-flowered subshrub whose virtues extend beyond its obvious beauty; for it is also important as habitat for a wonderfully-named genus of native moths, Notoreas.