Plant profiles > Rhopalostylis
Family : Arecaceae
The inhabitants of any country are often eager to proclaim their own forests as special in character, and New Zealand is no exception. In our case, one of the major characteristics that inspires such observations (in New Zealanders and visitors alike) is the luxuriance of many of our forests. Ferns, climbers, epiphytes, and various layers of trees and shrubs, confer an atmosphere more evocative of tropical forests than temperate forests of equivalent latitudes.
This effect is not only due to the structure of the bush, but is also derived from the presence of plants with tropical origins or affiliations; including the kiekie (a member of the Pandanus family), kawakawa (closely related to kava) and the world's southernmost palm. The nikau is New Zealand's only palm genus, and comprises two species, Rhopalostylis sapida and Rhopalostylis baueri. The latter occurs naturally only on the Kermadec Islands and Norfolk Island, but has been grown extensively in northern gardens on New Zealand's mainland. R. sapida is the species that many New Zealanders will have seen growing through bush in warmer parts of New Zealand.
As the only palm native to New Zealand, the nikau is a particularly conspicuous component of many of our forests. For obvious reasons, it has also become a very popular garden plant throughout much of New Zealand. Its natural range extends from the Far North to as far south as Banks Peninsula in the east, and Westland on the South Island's western coastline. It also occurs on the Chatham Islands, where it reaches its southern limit.
Rhopalostylis sapida has a wide distribution, and varies greatly thoughout its range (such that it is suspected that the Chatham Islands form may be a separate taxonomic entity). For this reason, horticultural selection has identified forms that are especially desirable for cultivation. Although some of these selected forms are certainly superior for garden use, it should be remembered that it is always ideal to utilise local forms for revegetation purposes. It is also advisable to attempt to locate a superior form from within reasonably close proximity to one's location. For example, within Auckland, the Great Barrier and Little Barrier forms are particularly attractive, vigorous forms that grow within a bird's flight of the city.
Perhaps the most impressive form that we have come across originates from the East Cape, where specimens have large fronds, substantial crownshafts and good wind tolerance. The last characteristic is an important factor in determining good garden forms, as plants from many parts of the country develop into somewhat battered, scruffy specimens in open conditions. The foliage of the Chatham Islands form of Rhopalostylis sapida is particularly resilient to wind and exposure; and accordingly, this has become a favoured form for cultivation in recent years. In addition to the aforementioned variant types, plants from the Waikanae area are also considered to make good garden plants.
Although they are tolerant of a range of tough conditions, nikau palms perform best when their roots are shaded by other plants. Like many coastal natives, they respond favourably to considerable amounts of fertiliser, and benefit from mulching (so that they are not overly stressed by dry conditions). They will only tolerate minor amounts of frost, although some forms are likely to be markedly hardier than others (the Banks Peninsula form, for example). Several authors have made the valid observation that nikau are particularly effective when planted in groups. When planted relatively close together, they form beautiful clumps of slightly arching trees, similar to how one occasionally views them within the wild.
The flowers and fruit are borne in impressive bunches, that are produced at the base of the crownshafts (when trees have reached maturity). The red fruits are avidly consumed by kereru, who are important dispersers of their seed. Another creature that is less familiar to most New Zealanders, the giraffe weevil, is another visitor to the nikau. These remarkable insects, which have extremely elongated 'snouts' (most notably in the case of males), feed on the flowers of nikau during summer1.
One cultural use that is worthwhile noting here is the application of nikau fronds as a roofing material by Māori and early European colonists - in a similar manner to the way in which palm fronds are used in many traditional tropical and sub-tropical communities.
- I am indebted to Gillian Driver for this information, and for helping me to see this feeding behaviour firsthand in the Waitakere Ranges. The giraffe weevil's ecological interaction with nikau is also noted in John Early's fine publication 'Know your New Zealand Insects and Spiders' (2009. Auckland : New Holland).