Lawns of Bluff

March 26, 2023

This article has been written by Marley Ford, with all images taken by Marley whilst working on botanical surveys within Southland. The full version of this article first appeared in NZPCN’s December edition of Trilepidea, and we would encourage anyone who wishes to read the unabridged version (in its full taxonomic regalia) to look up Marley’s original article.

Unexpected biodiversity is an interest of ours at O2, and Marley points the reader towards the fact that seemingly unpromising landscape types can be repositories for rare species and proxy habitats – in the style of Gonzo botany that we respect here at O2. And there are even some unintentional closeups of aggregate within Bluff footpaths for all the concrete enthusiasts out there.

Walking through the suburbs of Bluff to the historical cemetery in search of lichens, one is easily distracted. Within five minutes of walking, I was on my knees looking at herbs in the sandy-soiled lawns of Bluff, parallels of coastal turfs. What look like typical suburban lawns, in fact host a surprising variety of native plants, including rare species.

In places, native herbs such as Plantago triandra (shown below on the lefthand side of the first image) and the unnamed southern coastal entity of Chaerophyllum (a) (CHR 364086; “minute flower”, pictured below, right), dominate the turf.

Other common native low-growing herbs include a small-leaved form of Dichondra brevifolia agg. with large flowers (shown below), a purple form of Centella uniflora, the minute creeping Gonocarpus micranthus, Hypericum pusillum (with its conspicuous yellow flowers), Lobelia angulata (with a mass of flowers) and Hydrocotyle microphylla.

One uncommon herb of special interest was the small Acaena microphylla var. pauciglochidiata (pictured below) – a particularly exciting find as I’d been hunting for this species a few days earlier at Cosy Nook with no luck, only to find it growing on the footpath edge 25 metres from my accommodation in Bluff ! The larger Acaena pallida (classified as declining) was common in lawns, though often greatly stunted.

Slightly stunted forms of the ‘nationally threatened  Southland daisy Leptinella traillii subsp. pulchella (in the image below, left) were also observed as small patches in lawns. Looking very similar to the purple form of Centella uniflora was the coastal musk, Mazus arenarius (classified as declining, shown below on the right).

The weedy race of the nationally threatened herb, Geranium aff. retrorsum (a) (AK 299877; Canterbury, pictured below) is locally abundant in the longer lawns and is a great coloniser of disturbed ground. This race is currently regarded as indigenous and is differentiated from the rare truly indigenous form by the lack of turnip-shaped roots.

The native onion orchid, Microtis unifolia, was common in lawns that haven’t been cut for a while, and the sun orchid, Thelymitra longifolia agg., was much rarer. Various native asters occurred in lawns, the weedy Cotula australis, silver patches of Euchiton audax, and the new combination for the native cudweed Pseudognaphalium lanatum.

Native sedges dominate the lawns in places, the most common being the lime green Schoenus maschalinus and the often-copper-brown stunted Eleocharis acuta, with another stunted sedge, Juncus planifolius, scattered throughout.

Larger shrubs of mikimiki (Coprosma propinqua var. propinqua) and southern rātā (Metrosideros umbellata) were seen tortured to lawn height by the frequent mowing. In sprayed areas, the native liverwort Marchantia berteroana was seen growing en masse, and various native moss species were common throughout the lawns.

One particularly interesting frontage was found to host a diversity of native plants and some new southern records. Bluff is well known to botanists for its disjunct population of a rare, tiny, carnivorous sundew, Drosera pygmaea.

This species was found on the exposed sandy soils of a recent house build, along with a small, endangered, annual restiad, Centrolepis strigosa.  C. strigosa was very common in this lawn at the time of my visit, with more than 30 plants seen, and another smaller population was found in a different lawn close by.

While based in Southland for several weeks, my casual observations have revealed a total of 30 native plant species living in the lawns of Bluff, a third of which are threatened. Southland has its own distinctive coastal turf plant communities, encouraged in the past by the activities of seabirds along its coast. Often these plants are halophytes; able to withstand high salinity, the exposed conditions of the coast and trampling of flocks of seabirds.

Bluff’s lawns draw parallels, acting as a surrogate habitat to these natural environments, which have been greatly reduced in extent. The lawn communities are maintained by the plants growing in sandy soils being regularly maintained and cut low, the sound of which can be heard in chorus on the otherwise quiet Bluff weekends.

These lawns experience a range of conditions from cool and damp to often dry, hot, and free-draining. From a conservation and educational point of view, we should aim to incorporate all kinds of native biodiversity into our urban landscapes. Rather than monocultures of lawn made up of exotic grasses with low ecological benefits, inducing and encouraging native coastal turfs would increase suburban biodiversity.

At the very least, these lawn turfs could act as refugia for these plants in future – with their natural habitats potentially threatened by sea level rise.