An unstable existence

June 14, 2013

The nature of the geology along this part of the South Taranaki coastline was emphatically impressed upon me by my friend, Paul, with whom I had come to observe and photograph interesting local species. Paul advised maintaining a safe distance from the edges, as the uppermost sections of the cliff can give way easily, potentially leading to an unwanted encounter with the boulders 8m below.

Such concerns are clearly not shared by the vegetative inhabitants of these clifftops. Despite this zone’s unstable nature, it has the advantage that it is safe from competitors that would find this prospect too hostile to put down roots (including weeds like buckthorn, which was growing abundantly in the land behind the cliffs). A recently-described species of ‘native daphne’, Pimelea carnosa (pictured below), is one of the plants that specialises in this dynamic environment (similar to its relatives in other parts of the country).

Its specific epithet, ‘carnosa‘ (meaning ‘fleshy’), provides some information about its leaves, which are pictured in detail below. Having thick leaves is a common adaptation in coastal plants, for whom moisture retention is an important matter (in the face of the constant, desiccating effect of salt). This creeping, blue-leaved plant plays an important ecological role, as the larval host for a beautiful moth that is commonly referred to as Notoreas ‘Taranaki’.

P. carnosa grows in the company of another plant that is much more familiar to gardeners and landscapers, but whose story is not well known. Coprosma ‘Hawera’ (pictured below, left) has become a common sight in native gardens and public plantings, where it is utilised for the dense, green mats of foliage that cover the ground very effectively. I previously thought that it might have been a naturally-occurring hybrid, but Colin Ogle (who kindly shared his knowledge with me about plants from Taranaki to the Manawatu, and is the major authority on this form) informed me that it is a distinct, stable form which may merit recognition as a separate species.

It is acknowledged as such within Eagle’s Trees & Shrubs (2006), where it is included as Coprosma acerosa (iii). Within the supplement to that publication, it is noted as growing on hard substrates, in contrast with the loose, sandy habitats that typical Coprosma acerosa occupies, and it is also stated that the two forms grow close to each other in some locations (whilst remaining distinct). Bearing in mind those points, it would not be surprising if this plant is recognised as a new taxonomic entity in the future.