Subtle differences

November 6, 2016

The colour might be blue, the leaves may have a similar shape and size (and are just as densely packed), but the growth form of Pimelea orthia marks it out as a very different proposition to similar species like P. prostrata and P. urvilleana. The upright, mounding habit of P. orthia is particularly useful, as there are relatively few dwarf shrubs that can occupy an equivalent role within gardens; especially ones with Pimelea orthia‘s colouration.

This attractive plant was described as a new species within the revision of Pimelea that was published in several parts from 2008 to 2011. Although the assertion presented within the revision that P. orthia comprises two subspecies is not universally accepted (seemingly justifiably), the species itself has long been held to be a distinct entity, with Thomas Cheeseman naming it Pimelea prostrata var. erecta.

Cheeseman’s name provides the essential information for P. orthia‘s main point of difference – its erect growth form. This is also referred to in its official epithet ‘orthia‘, which is derived from the Greek word for straight (a term that endures within English in the adjective, ‘orthogonal’). A recent trip to Tairāwhiti/East Coast allowed me to see Pimelea orthia in several populations, including Mahia Peninsula (in the images at the top and bottom of this journal entry) and on roadside banks near Te Araroa (shown within the other three photos).

In our design work, we are always looking into the slight differences between species, for the distinctive qualities that they can provide to plantings. Prior to the description of P. orthia, the only commercially-available species of Pimelea that exhibited a similar form was a native of cold, dry areas in the South Island, called Pimelea traversii (a species that I have been fond of for many years).

It was therefore a revelation that we could use a Pimelea with similar qualities that naturally occurs in (and is accordingly well adapted to) the warm, humid north of the country. Its appeal is further reinforced by the fact that it was historically recorded as growing in Auckland City, where we have planted many specimens – grown by Oratia Native Plant Nursery from material originally collected at Kaipara.