New Zealand’s two species of Melicope are an emphatic example of the capacity of closely related plants to look wildly different to each other. Whilst wharangi (Melicope ternata) bears large, bright green leaves on a fairly conventional branching structure, poataniwha (Melicope simplex) is a more cryptic character that carries its tiny leaves on a densely interlaced framework.
Our two species of Melicope frequently hybridise within the wild, producing a range of variants that are collectively known as Melicope x mantellii. This loose entity consists of a spectrum of forms, some resembling wharangi more closely, while others are very close to typical poataniwha. Some valuable forms may be selected for cultivation from these; the most useful of which is perhaps a naturally-occurring hybrid from the North Shore that combines M. simplex‘s compact, upright form with M. ternata‘s vibrant, light green foliage (the leaves are about half the size of typical M. ternata).
Along with mairehau (Leionema nudum), our two species of Melicope are the only members of the citrus family to be present in New Zealand. As with other members of this family, both wharangi and poataniwha emit a pleasant scent (from oil glands) when the leaves are crushed.
Anonymity is a characteristic that is not commonly thought of as a positive attribute in a plant. We are usually sold plants based on one feature or another – whether they are flowers, bold foliage or a particular colouration.
However, the appeal of some species lies in how much they recede from our attention – as in the case of many of our small-leaved trees and shrubs. These plants provide a subtle counterpoint to other species (thereby heightening the effect of their neighbours), as well as lending greater depth to compositions. Like shadows, they convey a beautiful ‘nothingness’ that can instil a sense of calm into plantings.
Elsewhere, I have expressed the sentiment that it is interesting to track evolution in garden tastes – and its subsequent effect on our perception of certain plants. In just twenty years, Melicope simplex and its twiggy colleagues have transformed in our eyes from ‘curious shrubs’ that only merit attention as ‘collector’s items’ to plants that are worthy of wider cultivation1.
Interestingly, although she would have been considered out of step with the Zeitgeist of the 1970s, Muriel Fisher spoke favourably of poataniwha within her progressive work on native plants, ‘Gardening with NZ plants, shrubs and trees’2. Muriel’s observations on many plants have been shown to be remarkably prescient; and in some cases, those writings of the 1970s are still ahead of their time3.
With regard to poataniwha, Muriel made the dual observation that its overall form and resilience to a range of conditions (even unpromising clay) were two major attributes that weighed in its favour. This versatility is demonstrated above in images of two contrasting habitats in which Melicope simplex naturally grows; the open, sun-beaten marble outcrops of Takaka Hill (where its stems take on a lighter shade of red) and the much more sheltered environs of forest adjoining the Manganuku Stream in the Waioeka Gorge.
M. simplex differs from similar small-leaved shrubs (otherwise known as filiramulates4) in two key ways. Its leaf arrangement and branching is comparatively conventional – as opposed to the more ‘radical’ character of some filiramulates (for example, the zig-zagging form or weeping branches exhibited by some species). It also has dark, purplish stems, that give the shrub a distinctive appearance – especially when viewed in contrast with the bright (or pale) greens of neighbouring plants.
Its dense, upright growth habit makes it a particularly suitable candidate for an application to which many of our filiramulate shrubs are eminently suited – namely, their use as living climbing frames. The photograph higher up in the page shows Clematis forsteri (an attractive native cimber with scented, cream flowers) twining its way through poataniwha.
Although M. simplex can develop into a small tree exceeding 4m in nature, it is best maintained as a more compact shrub within gardens (anywhere between 1.2 and 2m). In this capacity, it can play a valuable role in forming part of the structure in a garden, without attaining an excessive height. Trimming with secateurs is more advisable (than hedge clippers), so that plants retain a naturalistic form.
It grows throughout most of the lowlands of New Zealand’s two main islands, occurring predominantly in scrub and forest margins (although it readily abides an open aspect). There is a form from the ultramafic cliffs at North Cape, that exhibits a more stunted, spreading habit (this may come to be considered a distinct variety, if the work is ever carried out on it)5. In spring and early summer, poataniwha produces small whitish flowers, that are very popular with small insects, including native bees and hoverflies6. In autumn, the fruits open to reveal the distinctive, glossy black seeds that are pictured above.