Nikau: stalwart of the south

At this time of year it is easy to think of places in the sun, places we like to escape to. The quintessential plant of the tropics is the palm tree. The most important of these is the coconut palm, a true icon and it is not found outside the tropics. Its slender trunks and swaying fronds line most sandy beaches in the islands. But it’s not an altogether innocent tree because its falling nuts can injure people who seek their shade. In our climate, though, there are many palms which are well suited to evoke the tropical escape. Not least of all, the native nikau, Rhopalostylis sapida. Even within the range of the New Zealand geography there is quite some variety in its form. On the Chathams, the nikau has rather more stout trunks and a robust crown shaft. This population, which is now confined only to Pitt Island, consists of only 70 specimen and is under threat. It is also the most southerly occurring species of palm in the world. Further to the north is a population on Little Barrier Island where the variant is larger in all proportions than those of the mainland populations. Here the trunks may grow up to half a metre in diameter! Intermediate between the Little Barrier Island palms and the mainland group are those of Great Barrier Island. Further still to the north, on the Kermadecs, is another nikau. This one however has been put into a separate botanical group, Rhopalostylis baueri var. cheesemanii. syn. R. cheesemanii, R. baueri var. kermadecensis. So now with its botanical identity established it can be described as a more robust species than the New Zealand nikau, with a larger crown shaft of fronds of a more arching nature and largely more tolerant of wind. In my observation the New Zealand mainland species of nikau R. sapida, found flourishing in the bottom of gullies, is less well adapted to the environment above the canopy of the forest. Once exposed to the elements the fronds tend to burn and look a little tatty. For our purposes, the old saying ‘right plant in the right place’ must be observed. There is yet another member of this genus, from Norfolk Island, the Norfolk nikau, R. baueri var. baueri, which I have never seen it advertised for sale.

Now is a perfectly good time to be planting palms as long as they are given plenty of mulch and not fed until they commence into their summer growth. While the palms are dormant it is inadvisable to feed them as the roots are easily damaged at this point. Once new fronds start to unfurl is a good time to be feeding, the plant is growing and will take up and use the nutrients supplied. Nikaus especially will benefit from timely feeding, increasing their rate of growth substantially. In the wild nikaus are notably slow to form a trunk, taking up to thirty years before it begins to emerge!

While on the topic of sunshine, I have in a pot on the deck some Cape cowslip Lachenalia aloides ‘Aurea’. These bulbs from South Africa, as the common name suggests, are an old fashioned favourite. Whose grandmother didn’t have a row of them at the front of their garden bed? Well mine were given to me by a friend, not my grandmother, but each year they multiply and intrigue me from the first emergence of the green and red mottled leaves in autumn to the striking yellow and red flowers during the dark days of winter. Thank you, Greg, for this gift I always enjoy them, a splash of sunshine during rainy days.

The charms of dusk

Recently I was asked about how to combat morning glory, Ipomoea learii a common weed in many parts of the island. My advice was as follows; firstly clear as much of the vine as possible physically. Once this is done allow it to start regrowing and when it is in the flush of regrowth spray it with a systemic herbicicde, that is one that circulates to all parts of the plant. Hopefully in this way you will have success in killing this rampant vine. Letting the vine begin to regrow means the poison will be more successfully translocated to all parts of the plant.

Alternatively for those who do not wish to use poisons I would suggest removing as much of the vine as possible, at least this will allow any existing desirable plants a chance of re-establishing themselves. A follow up to this treatment would be the placement of impenetrable mulch such as old carpet, following which eternal vigilance is necessary to over come such a pest.

There are two other members of this genus which are not of an invasive nature. Firstly is powhiwhi, Ipomoea palmate syn.I.cairirca, as I have mentioned in my last column, a vine with purple flowers and as the name suggests palmate leaves. This vine is naturalised in Northland and it is uncertain whether it was introduced by the early Maori or whether it is naturally indigenous to these parts. Either way I am happy to have it in my garden. The other is the moon flower, Ipomoea alba syn. Calonuction aculeatum, C. bona-nox, I. noctiflora. This climber, a perennial, has large 10cm wide white flowers with most delicious scent. They open their blooms at dusk, an intriguing event to witness as the buds swell and burst open before your very eyes. This will be planted in my scented garden next to a seat where the spectacle can easily be experienced. Plants can be easily propagated from seed. I once had one grown in a pot on a balcony where it was a star performer.

Another white night scented and flowering plant is the orchid cactus Epyphyllum oxypetalum ‘Belle de Nuit’. As its name suggests it unfurls its flowers at dusk to release its scent for many metres around. The flowers are creamy white with sometimes a hint of pink. The leaves are modified into tiny spines and the stems flattened and leaf like. In their natural habitat of Central America they are largely epiphytic, growing on other trees and shrubs. They are therefore suitable plants for pots or hanging baskets where in the latter the stems will tend to bend downwards as if to afford the viewer a better vantage point. How I am anticipating the warm summer evenings in my night scented garden!

Now just a brief pedantic note about the attention to detail the BBC goes to with its dramas. In their collaboration with HBO on the drama ‘Rome’ I noticed a flaw in the use of plants in Atia’s atrium, There were specimens of both lobster claw, Heliconia sp. and Philodendron sp., both of which come from Latin America, were the Romans really the first to the Americas? Never mind I am enjoying the series anyway!

Black Eyed Susan

Water tanks are to my mind unavoidably ugly, requiring a disguise at the soonest possible opportunity. To effect this I have, as I have already mentioned, planted golden rain vine, Pyrosteria venusta and the blue sky flower vine, Thunbergia grandiflora, with as the name suggests sky blue flowers up to 5cm across. To party with these two, growing of its on volition elsewhere in the garden, I have black eyed Susan, Thunbergia alata. This vine is very easy to grow, and will start from seed. The flowers are 3cm in diameter, orange and sport a ‘black eye’ at the centre. I hope, in the company of the other two, and with a native purple convolvulus Ipomaea palmata, will all soon be romping over the water tank, keeping it cool in the summer and screening it from view by the front door.

The genus Thunbergia is comprised of some 100 species ranging in habitat from tropical Africa to tropical Asia, including India. They were named for Dr. Karl Pehr Thunberg, 1743-1822, who travelled through Batavia and Japan before returning to Sweden where he became Professor of Botany at Uppsala. Many of them produce showy flowers hanging on long racemes below the foliage. Of these I once grew the scarlet clock vine, Thunbergia coccinea a native of India and Burma (Myanmar). My vine threw itself to the top of a tea tree from where it dangled it long racemes (up to a metre long) of red flowers over the driveway. I bought it in a wee nursery in East Tamaki (no longer there) and have never seen it advertised for sale since. Another Thunbergia Lady’s slipper vine, Thunbergia mysorensis, also hangs its flowers on racemes below the canopy. The flowers are rusty red in bud and open out with reflexed petals of yellow, the whole looking very exotic indeed. There was a vine growing in the Auckland Domain at the winter gardens on the pergola adjacent to the tropical house, whether it is still there or not is doubtful as last time I was there, staff were replacing the pergola and the vines were in large piles on the ground!

Thunbergia grandiflroa var. alba, a white form of T. grandiflora, is another with flowers performing at the end of a dangling raceme. I the great fortune of finding this lovely vine recently, after only ever seeing it in a book on gardens of the tropics. This vine is destined to clothe a ragged old wattle tree. The intention is for the flowers to hang down above the heads of visitors as the wander beneath.

On the bank below this I plan to plant some nikau Rhopalostylis sapida, a couple of which I have struggling valiantly for their lives in pots on the deck. It is well time they were released into the garden! Coupled with these I think clumps of cabbage tree Cordyline australis, would work well. There are a very large number of different forms of cabbage trees available and since I plan on planting here a pink hibiscus Hibiscus X ‘Agnus Gault’ I think maybe a clump of red cabbage trees might do well along side her!