Pseudowintera

A basic lesson in evolution is useful for understanding where our horopito sits within the grand scheme of the plant kingdom. From humble beginnings (as a sort of primordial scum), plants have evolved into a suite of increasingly specialised growth forms. At the pinnacle of this stand the flowering plants (or angiosperms) – the group of plants that now dominates the Earth’s surface.

It is here that horopito fits in to the story, for Pseudowintera is considered to be a very primitive flowering plant. This is partially evidenced by the simple, unspecialised flowers that horopito bears, as well as its wood structure (which is unusual in being similar to that of conifers, rather than the majority of flowering plants¹).

The four species of Pseudowintera are found only in New Zealand, in a wide array of habitats. The most commonly-known species (by virtue of its colourful, mottled leaves) is the mountain horopito, P. colorata. The lowland horopito, P. axillaris, is the next most common species, whilst the two remaining horopito species, P. traversii and P. insperata, are restricted to relatively limited areas within the wild (particularly the latter).

In recent years, the name of horopito has extended beyond botanical and gardening circles, and entered the lexicon of cooks throughout the country. The reason for this is hinted at in another of its common names, pepper tree.

The spicy flavour of the leaves has long been known to Māori, although it is difficult to know whether it was actively used within cooking – it was certainly used to treat various conditions, in addition to the slightly uncharitable purpose of weaning children off breastfeeding² (I imagine the peppery taste was quite effective). Māori also traditionally attached an interesting spiritual belief to horopito; whereby its leaves are worn by the souls of the dead – on the way to, and within, the afterlife².

Despite its growing popularity as an ingredient in condiments and cooking, horopito’s peppery flavour is not a great hit with the many introduced mammals that ravage the plant life of our forests. The fact that animals like deer find Pseudowintera unpalatable often results in a particularly high abundance of horopito in areas that are heavily browsed by pest species³.

One interesting creature that has developed a special association with horopito (specifically Pseudowintera colorata) is a tiny native spider, called Lamina minor⁴. These rather beautiful little spiders are green in colour, but also bear light purplish-pink markings that help them to blend in with the leaves. Their most remarkable feature is their translucent skin, which on close inspection permits the viewer to see their beating heart.

Of the many botanical discoveries from recent years, the Northland horopito is one of the most horticulturally exciting. Some threatened species have the good fortune to possess especially good looks, making them more likely to receive attention (and assistance) in their plight for survival.

And the critically endangered Pseudowintera insperata is certainly a plant that requires our attention. In 2011, only about 50 adult plants of the Northland Horopito endured within the wild, in the limited area (on the northern side of Whangarei Harbour) where it is mostly naturally found⁵.

In visual terms, P. insperata is most closely affiliated with P. axillaris, which has similarly attractive, shiny green leaves and eventually grows to become a small tree. The underside of the leaves on both species exhibits a feature that is universal to all of our horopito, but is especially striking in P. axillaris and P. insperata – which is a white colouration that creates interesting flashes of colour (as plants shake in the wind).

However, there is a marked difference in the shape of the leaves (a distinction that is very apparent, even from a long distance). P. insperata has more rounded leaves that terminate in a blunt tip (often with a notch in it), as opposed to the sharper leaf tips of P. axillaris.

Although capable of reaching 7m in the wild, Northland horopito is more likely to reach a height of between 2 and 3m in the garden. It withstands pruning well, and could even be maintained at a much smaller size of 1.2m – if its role within a planting dictates a more compact form.

P. insperata has proven to be adaptable to a range of conditions within cultivation. The main site where plants have been tested is the grounds of the main Auckland University campus, where it is planted in both high light and dense shade. It deals well with both aspects; which is unsurprising, considering the capacity of other Pseudowintera species to achieve maturity in deep shade⁶, and the variety of habitats in which P. insperata endures (from cool forest near the summits of Mt Manaia and Bream Head) to exposed scrub. In the wild, it generally occupies sloping sites, and as such benefits from well-drained conditions in the garden.

It has tremendous potential as a shrub for evergreen structure; due to its orderly appearance, beautiful foliage, and reddish stems. This potential may become realised in the coming years as Pseudowintera insperata becomes available for use within gardens. This brings me to one final point regarding the use of P. insperata within gardens. It is sometimes advisable with endangered species to plant them in isolation from other members of their genus, so that they do not hybridise (thereby maintaining the integrity of the wild plants).