Toronia

Although examples of the differences between our natural history and that of Australia are not in short supply (such as the total lack of cycads in New Zealand, and that whole marsupial business), the Protea family is a particularly illuminating case in point. Whilst this predominantly Southern Hemisphere family is represented by around 900 species within Australia, New Zealand has just 2 proteaceous species – namely, rewarewa and toru.

It is interesting to reflect on how outliers such as toru register within our landscapes; especially in light of the varied paths via which plants have ended up on our shores (whether from ancient Gondwanan origins, descending from the tropics, or crossing the ditch from Australia). I often feel that toru has an ‘exotic’ air to it when viewed amidst more familiar members of the New Zealand flora.

Toru’s narrow, red-tinged leaves and upright, flame-like form are most likely to be encountered in places with conspicuous similarities to the kinds of environments in which the family has multiplied into a vast array of genera in Australia and South Africa – such as dry woodland habitats and infertile ridgelines with comparatively sparse vegetation cover. It makes sense that it is also a typical associate of kauri forest, given the infertile soils that develop within these forests.

Toronia toru is the sole member of its genus, with its Māori name reflected in both the generic and specific parts of its botanical name. It was formerly included within the genus, Persoonia; the title by which it is frequently found in many older works of New Zealand botany.

Lawrie Metcalf provided one of my favourite horticultural descriptions within his well-known book on New Zealand’s trees and shrubs, in which he noted that toru’s open flowers “vary from Barium Yellow (503) to Straw Yellow (604)”. Setting aside the comparatively anodyne adjective of ‘straw yellow’, my mind immediately drifted towards just what constitutes ‘barium yellow’.

As it turns out, barium yellow is the colour of a pigment, barium chromate, that was used in painting, along with the even more alarmingly-titled strontium yellow (and zinc yellow). In Metcalf’s case, the use of such specific descriptions for colour betrays his background as a breeder of plants (in addition to being an acute observer of natural species) – a pursuit that requires much greater attention to detail than most people afford to the consideration of colour. This is reflected on an even finer scale in Metcalf’s description of the filaments of one Hebe variety as ‘Rose Bengal’.

What does most of this detour have to do with toru’s potential within landscape architecture and gardening ? Not much, really, other than to comment on the level of rigour (with respect to the observation of colour) exhibited within the seemingly disparate worlds of plant breeders and 19th-Century artists.

For horticulturists, toru’s foliage colour (and tone), well-behaved growth form and floral scent are more likely to be motivating factors in favour of its cultivation. When viewed in association with more subdued characters such as manuka, Corokia buddleioides or Halocarpus kirkii, toru’s vibrant green, linear leaves project forth visually – much as they do in plantings where similar contrast is established.

With respect to contrast in both natural plant communities and designed environments, it is interesting to consider the subject of leaf size in more detail. Members of our flora exhibit a very wide array of leaf sizes, with this diversity often apparent within a single plant community.

Observation of the interplay between varying leaf sizes and characters informs the work of gardeners and landscape architects, with informal adjectives (such as bold, fine or willowy) being used to describe these variations.

In the early 20th Century, a classification system was formulated by a pioneering Danish botanist, Christen C. Raunkiaer, for categorising leaf size. This was discussed with respect to our flora in Peter Wardle’s excellent work, ‘Vegetation of New Zealand’¹, with plants assigned to classes ranging from megaphylls (to which nikau’s and tree ferns’ large leaves conform) down to leptophylls (which describes most of our small-leaved shrubs). According to Raunkiaer’s criteria, Wardle designated Toronia toru within the category of a microphyll, similar to kauri and pohutukawa.

Clearly, I’m not envisaging that all and sundry are about to start referring to mesophylls and nanophylls on a regular basis (I suspect that Rob Champion and I are part of a very small demographic who might). That said, the value of having a more comprehensive way of thinking about the varying textures of plants should seem self-evident for those of us who are concerned with creating plantings with richness and depth.

As noted previously in this profile, Toronia toru is associated with well-drained habitats, and therefore requires good drainage to thrive within cultivation. Whilst it is generally fairly rapid in growth, I have seen one specimen grow at a comically slow rate (in very poor soil) that could only inspire admiration – for the audacity, resilience and general indifference that it displayed during its fabled establishment. Toru’s eventual size generally sits somewhere between 2.5 and 4m, making it a fine tree for urban environments where its compact dimensions are especially useful.

The species was first collected for Western Science (in contrast with the fact that Māori already had considerable pre-existing knowledge of this and other members of our flora) by Allan Cunningham in 1826 – during his time exploring and botanising the north of New Zealand. It occurs in a range of habitats (from coastal to montane forest and shrubland) from the Far North down to the central North Island.