Nikau Palm Blues

Everything you need to know about the Shaving Brush, or Nikau palm by transplanted Kiwi, Charles Jackson.
Charles S. Jackson, Westcliff on sea, Essex, UK
Chamaerops No.34 Spring 1999

Picutre: The bulging crownshafts of Rhopalostylis sapida, Jim Wright's garden, California.

Rhopalostylis sapida is often considered a challenge to grow in Europe and so, as a New Zealander, I thought it would be useful to examine its natural habitat, climate and cultivation requirements to assist my fellow palm enthusiasts to grow one of the world's most beautiful temperate palms. Rhopalostylis Sapida grows in New Zealand, its off shore islands i.e. Great Barrier Island and also is found on the Kermadec Island group, Norfolk Island and the rather southerly Chatham Islands.

This palm species is found nowhere else in the world and, like most New Zealand plants, has very strange growth habits and rather contrary requirements. Even on mainland New Zealand they will grow in some places but will not grow in others even if the climates are similar. This palm is predominantly a coastal lowland tree but in favourable climates can be found growing further inland but not far! Its southern limit on the mainland is Westport on the very wet, mild west coast of the South Island. Why this palm will not naturally grow further south than Westport is unclear as the climate is very similar in Westland all the way down to Haast (Jackson's Bay) but there must be some slight climatic or physical change south of Westport which precludes this palm from spreading. It is planted as a garden shrub in Hokitika and Greymouth and grows marvellously so it can only be assumed that it must be the physical barrier of the hills between Westport and Greymouth that prevent this palm from naturalizing areas further south. Alternatively, it could be a slight climatic difference as already mentioned but this difference must be minuscule.

As for the colony of Nikau palms at Palm Gully, south of Akaroa on Banks Peninsula on the east coast of the South Island near Christchurch, it is not at all certain that this is a natural population. It could very well be a remnant population from when the Banks Peninsula and all the Canterbury plains (and virtually all of New Zealand) were covered entirely by native evergreen, hardwood forest. Long before the arrival of the white settlers the Maori tribes of New Zealand had cleared by fire large areas of forest and the Banks Peninsula tribe had, of course, done the same.

If it is a natural palm colony then this would be the southernmost limit of a mainland population of this species and also the most cold adapted and dryness adapted variety of Nikau available anywhere. Although the nikau of the Chatham Islands lie further south than the Banks Peninsula population, there are significant differences between the climates of the two locations. The Chathams have a temperate ocean climate that is neither too hot nor too cold. In fact the Chatham Islands do not suffer any frosts whatsoever but then have a great deal of cool weather to put up with. Constant sea breeze blows at all times and frequent violent southerly storm fronts blow through all year round.

On Banks Peninsula some of the climatic conditions affecting the Chatham Islands are experienced by the Nikau population in Palm Gully but the problem of frost, dry summers and strong sunshine are added to make life for these palms considerably more difficult. Nevertheless, they are probably the best and most robust type of Nikau to be found in mainland New Zealand. Seconded only by the West coast South Island type, closely followed by the type found near Gisborne (East coast, North Island) and the superior type found on the Great Barrier Islands (Northeast of Auckland).

Regarding whether the Banks Peninsula Nikau palms are naturally occurring, it may never be known. It has been suggested that the Maoris, when they migrated south from the North Island, brought seed of palms with them to grow for their own use. It has also been suggested that these palms were planted in the massive reforestation programme undertaken by Christchurch Botanical Gardens and Christchurch University at the beginning of this century. It is interesting to note that the New Zealand people were vigorously encouraged from the 1880's onwards, in various campaigns, to go out and replant as much native vegetation as they could to help restore New Zealand's beauty after the terrible ravages of the Maori bush fires. Anyway, the Nikau population at Palm Gully, exists and survives brilliantly, and does not seem to be bothered too much by the colder conditions or even the occasional snow cover on the high volcanic peaks of Banks Peninsula and Port Hills which overlook Christchurch and Lyttleton Harbour.

Regarding Nikau's adaptability to different temperatures, it is very evident by examining trees in different locations and at different latitudes that these palms do not like hot climates or strong ultra violet light. As you move further north in New Zealand the quality of the trees deteriorates somewhat, from the good specimens found around cool Wellington, the capital, to Auckland and North Auckland where they are the poorest type specimens seen anywhere in New Zealand. Auckland and further north have a warm temperate climate with very strong sunshine leading to rather a harsh environment which sustains mangrove swamp and coarse, woody vegetation and sustains tree ferns and Nikau palms only where it is shaded, sheltered, cool and damp.

As you examine the Nikau palm population going south to the cooler climates, you make a rather interesting discovery. The Nikau's fronds open out more and more the further south you go starting with the Auckland /Northland type which have the most upright fronds (possibly to protect themselves from too strong sunlight). Further south are the noticeably more beautiful southern type from the southern North Island and the South Island whose fronds open out to a full 45° angle. There are exceptions to this rule as the Gisborne and Great Barrier palms have fronds that open wider than other near populations. It is also worth noting that even the Norfolk Island and Kermadec Island Nikau's have more open fronds even though these islands are in the sub tropics but due to their oceanic cool, cloudy climates they sustain Nikau growth better than the majority of northern New Zealand.

It would be interesting to find out whether the Nikau was indigenous to New Zealand before the Maoris arrived or did they in fact bring this palm with them from Norfolk and Kermadec Islands? I believe that the Nikau was already there and had been for many hundreds of thousands of years. Perhaps there is ancient fossil evidence in New Zealand showing Nikau frond impressions from thousands of years ago. The differences between the island Nikau and the New Zealand mainland type are significant enough for me to think that they have always been different populations.

The Maoris found this tree very useful for all sorts of purposes. It must have been a godsend to them that their new land was endowed with such a beneficent tree or that the tree they had brought with them from the Pacific Islands could indeed grow in this rather cold, wet southern land. Anyway, this is besides the point - the Nikau is there, and in a myriad of shapes and sizes. It is truly the most temperate of all palms and this means that it dislikes heat and equally dislikes cold and will only succeed naturally in the most temperate range of latitudes (3O°S to 44°S). It is planted as a garden tree elsewhere in New Zealand outside these latitudes but it can be risky as heavy frosts precludes any cultivation. The only exceptions I know of are at the mild Glen Falloch Gardens on Otago Peninsula at Dunedin and , of course, at Greymouth and Hokitika in west coast, South Island where heavy frost is not normally a problem.

Dryness of climate is also a great limiting factor that makes it impossible to grow Nikau palms in my home town of Timaru, Canterbury province or indeed in Christchurch the provincial capital. Added to the dryness of the Canterbury climate is the relentless heavy frost experienced every winter that would decimate a Nikau population but tends to have no effect whatsoever on the local Phoenix canariensis population. Dryness and frost are also what precludes Nikau from spreading to inland New Zealand and in north Auckland the very salt laden sea breezes put pay to any chance of Nikau surviving in any decent looking state at all.

As for the Nikau palms requirements for cultivation, it is advisable to examine its various habitats. Firstly, they are deep shade forest trees which spend most of their lives under the high evergreen canopy of the native forest where they will experience no sunshine (Nikau palms burn even in dappled sunlight when immature), little wind and no frost at all. They grow in very moist rich leaf litter on the forest floor and don't mind even if the soil conditions are boggy. Some Nikaus live and survive quite happily in low scrubby na tive bush between 6 - 12 ff in height and, when young, are cushioned from the elements in the same way as the deep shade forest trees but in this short scrub they seem to have to grow, harden and mature much more quickly. Environment-wise, Nikau are awkward but reasonably adaptable even though it seems begrudgingly. True, the immature deep shade forest palms are impressive - deep green foliage, huge juvenile fronds both tall and wide but their scrub grown counterparts, which have to maintain much smaller immature dimensions so as not to overdo their exposure to the elements and damage themselves, are just as impressive.

Nikau palms are slow growing and this can sometimes be an understatement as generally the mainland type in cultivation will manage just one frond a year - two if you are lucky. The Island species, be it Norfolk, Chatham, Kermadec or Great Barrier are indeed faster growing - the Chatham Islands type probably winning this race outright. It is said that they start growing a trunk around 15 years of age shortly after having started to produce the first of the adult fronds. Nikau do have two frond growth stages - juvenile fronds which are not hardy to frost, sunlight, wind, and the fully fledged adult fronds which are produced prior to reaching an exposed level in the forest or breaking through the overhead bush.

These palms are literally tortoises of the palm world and I would think it lucky to get a trunk on a tree at 15 years of age. It is more likely that you will have a proper Nikau looking palm tree at the age of 30 years at which time it will also flower. I have a friend who collected seed of an Auckland Nikau type and germinated it here in the UK in 1985 and his Nikaus are even now, in 1999, still only half the size required for trunk formation. It does depend, of course, on the environment you give your plants but even so the rate of growth is painfully slow. The large trees that are seen growing in New Zealand are perhaps 30 - 40 ft tall and must be in the region of 80 - 120 years old. By the time they reach this maturity there is nothing adverse that the New Zealand climate can throw at them that will do any harm at all.

Once a trunk is formed then growth does speed up and these trees seem to be able to adapt their growth rate accordingly to the height of forest canopy or scrub above them. Growing in short scrub they mature earlier - in deep forest they mature slower. However, don't make the mistake of thinking you could get your own Nikau to mature earlier if you move it out to a much brighter position. As juveniles they must at all times be in the shade with no sunlight at all. They must have a good level of light and dislike total shade but will withstand deep shade as long as the period of light is lengthy. My own experience has shown that they must be grown just like a maidenhair and have the exact same requirements of cool conditions, moisture, free air movement and no sunlight.

It is not a good idea, generally, to grow Nikau in hot houses as they can not cope with hot, humid tropical conditions and will simply cease growing. They can however be grown in a cold greenhouse with much ventilation in summer and considerable shading of the glass overhead. Not only, as mentioned earlier, will juvenile Nikau burn badly in sunlight but they will also be badly affected if there is too much bright light generally. When this happens they will go yellow and stay yellow in growth unless further shading is provided. Good air movement is essential for both juvenile Nikau and mature ones alike. It has been shown that the Island type of Nikau is superior to the normal type and this makes me believe that the flow of moist fresh air around the island plants is essential to their well being. So this must be provided when growing them indoors or in a greenhouse. Stagnant air will kill Nikau palms as it leads to mould, rot and general deterioration of growth and health. Nikau palms are also prodigious feeders, and I have found that they respond well to "Tomorite" tomato food and top dressing of fish, blood and bone. This greens up the fronds to a good deep colour and also works well for all other species of palm.

Finally, although this article may portray the Nikau as a challenging palm to grow, please be assured that even though they may be peculiar, they are certainly not difficult trees to cultivate, and when larger are one of the most beautiful palms you can grow. They are absolutely perfect for indoor cultivation away from central heating and sunlight. Remember treat them like a fern and you will have no problems, and please also remember that it is unlikely that you will be able to grow this tree outdoors in your garden in the UK until fully mature or unless you live in a very warm, sheltered part of the British Isles where frost is almost never a problem.

 

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