The three New Zealand species of Corokia (and the numerous hybrids occurring between them) are widely used as garden plants within New Zealand. This is due to their often spectacular flowering and fruiting, and their bushy nature (which makes them especially appropriate for use as hedging or structural planting).
All three species bear small star-shaped yellow flowers at various stages over the summer, often in great profusion. The yellow is especially striking, as it contrasts against the usually muted tones of their foliage. Of the three species, Corokia cotoneaster has the widest natural distribution, occurring throughout New Zealand (in a multitude of forms) from sub-alpine scrub through to coastal cliffs. Corokia buddlejoides occurs solely in the northern half of the North Island (where it sometimes hybridises naturally with C. cotoneaster), whilst C. macrocarpa occurs naturally only on the Chatham Islands (in isolation from the other two native species).
The distribution of the genus is intriguing. It was long considered to be endemic to New Zealand, and a part of the dogwood family (Cornaceae). However, in recent years, botanists have ascertained that there are three species of Corokia which occur outside of New Zealand; C. carpodetoides from Lord Howe Island, C. collenettei from the far-flung Rapa Island (in the eastern Pacific), and C. whiteana, which is confined to a single mountain range in New South Wales. The other genus within the family, Argophyllum, occurs in Australia and New Caledonia.
This widespread species derives its specific name from the resemblance of its berry-laden branches to the members of the European genus, Cotoneaster. However, I would compare the brightly-coloured berries as being more reminiscent of a holly in berry, for they have a depth of colour that surpasses the often dull hue of cotoneaster berries.
The variety of berry colours possible within a single population is remarkable. I have observed scrubland at Pukaki (near Mt Cook), in which swathes of Corokia cotoneaster bore copious displays of red, orange and yellow berries (pictured at the base of this profile). This autumnal spectacle transforms the muted sub-alpine landscape, whilst also undoubtedly fulfilling an important ecological function in the provision of food to native birds and lizards.
Corokia cotoneaster is a useful and versatile garden plant. Its tight growth habit makes it suitable for hedging, from as low as 300mm high up to 2m high. Because the flowers arise both on the axils and ends of the branches, it rewards one with flowers even when clipped. Aside from hedging, it also has considerable potential for use as topiary, whether in a strictly formal sense, or in the more informal manner in which we have employed this species in gardens.
The foliage is typically a dark greyish-black colour, but this varies, with light green, olive and reddish-foliaged forms present in different parts of the country. Its growth form varies depending on which conditions it experiences within nature. Plants within northern coastal scrub can become tall, arching shrubs or small trees, whilst plants from open coastal or subalpine habitats typically retain a tight, pseudo-clipped appearance.
An extreme adaptation is that exhibited by the form present on the highly toxic, ultramafic (commonly known as serpentine) soils of Hikurua / de Surville Cliffs at North Cape. This form is one of many native species which has adapted a creeping habit, in response to this challenging habitat. The plants in the image directly below are from a variant known colloquially as Corokia cotoneaster ‘Paritutu’, which bears larger leaves, flowers and fruits than other forms (as well as always having yellowish-orange fruits).
As with other filiramulate shrubs1, its shadowy appearance provides a dynamic contrast with more conventional garden shrubs, and also associates well with the solid forms and planes of modern architecture. An unusual application towards which C. cotoneaster is exceptionally well-suited is bonsai. The Auckland-based artist, John Lyall, has made some outstanding bonsai specimens, in which the tortuous form of this species replicates the character of gnarled old pohutukawa or totara (in miniature). The small leaf size is also of obvious advantage for bonsai.
C. cotoneaster was described by Etienne Raoul, the early French surgeon-botanist who sailed to New Zealand with vessels sent to aid in the French settlement of Akaroa in the early 1840. Raoul described the species off specimens from the Akaroa coast.