As our closest neighbour, it stands to reason that we should have a fair amount in common with Australia. This extends to our flora – in particular, the plants and ecologies of the upper North Island, where our only member of this predominantly eastern Australian genus occurs. Some gardeners will recognise our species more readily by the name of Phebalium nudum. That is because all of the species in this relatively recently created genus of shrubs were previously included within the Australian genus, Phebalium.
The mairehau is one of several native species that, despite being repeatedly lauded by gardening authors, has never become widely cultivated. This is partially due to a somewhat unjustified reputation for being temperamental in cultivation. However, its anonymity is better attributed to the limited focus of the gardening and landscaping industry, which has for many years been more concerned with producing endless permutations of artificial Pittosporum and Coprosma cultivars than introducing New Zealanders to the full range of their natural heritage.
As mentioned above, mairehau has garnered a reputation for being tricky in the garden. This is understandable when one considers its natural habitat – which is usually kauri forest or sloping ground (plants of kauri ecologies are often cryptic in their requirements). However, my own experience of growing this plant has shown it to be amenable to normal garden conditions; and furthermore, the Pukekohe-based plantsman, Terry Hatch, has grown many mature specimens with ease – in conditions that could hardly be termed ‘specialised’. In his important work on the cultivation of native trees and shrubs, Lawrie Metcalf does not identify mairehau as being particular in its needs1, and neither did Leonard Cockayne nor Muriel Fisher2 when writing on the subject.
An observation that I have made regarding the cultivation of some plants from similar habitats to those that L. nudum frequents (such as Astelia trinervia or Alseuosmia macrophylla) is to provide fairly equable conditions in the garden – that is, try and reduce the fluctuations that a plant is subjected to.
Good drainage is obviously of importance to a shrub of sloping ground, whilst extreme drought should be avoided (in the case of the latter circumstance, various species of Olearia are especially useful). Large quantities of fertiliser are also likely to produce imbalance in soil conditions, and mairehau does not seem to require significant fertility.
However, the most important piece of advice in this regard is to plant specimens where their roots will be shaded (even plants from apparently tough scrub habitats will often have a degree of shade upon their base). This negates the effect of extreme heat or light upon the soil. Finally, it should be noted here that there is often an improvement in the performance of plants when they are propagated off stock that has been in cultivation for one or more generations.
Mairehau really is a plant that is deserving of much wider attention. In addition to its beautiful white flowerheads (which appear in early summer), the light green foliage is graceful and it has an especially useful scale (the medium-sized shrub is a category of plant that is ideally suited to the scale of most gardens). Its delicate, vibrant green foliage (borne on red-tinged stems) contrasts well with either the finer form of our many small-leaved shrubs, or the darker green, bold foliage of shrubs like Coprosma lucida.
Both the flowers and foliage of mairehau are scented, with the perfume in the leaves deriving from oil glands. Traditionally, Māori utilised the perfume by rubbing leaves on their bodies, whilst the leaves were also used in burials3. The former use is not, however, to be recommended – as some people can have a bad reaction to the oil, when exposed to sunlight4.
Leionema nudum occurs naturally from Te Paki in the Far North to as far south as Kawhia (in the west) and the Kaimai Ranges (in the east). It was discovered to science by the early missionary and botanist, William Colenso, in the vicinity of Whangaroa, in 1838.