Sunday, January 25, 2009
It is one of the quirks of history that our gardening ancestors learnt their craft in the cold lands of the Northern hemisphere. The plants they most valued were those they were most familiar with – the Rhododendrons, Camellias, and roses.
We have followed the tastes of our British founders, to a large degree, when it comes to the garden. I wonder how different our gardens would look if we came from a different gardening heritage.
Take our fascination with the Rhododendron. It is regarded by many gardeners as the ultimate tree or shrub. It is available in a wide range of colours, it is dependable, some varieties are a challenge to grow, and it is delightfully evergreen.
But if we inherited the gardening traditions of another, warmer clime, I wonder whether we might not be cherishing another plant that we tend to be a bit pretentious about – the wonderfully flamboyant tropical Hibiscus.
Among the many species and hybrids of this wide-spread genus, there must surely be the loveliest of all the summer flowering shrubs for the New Zealand garden, with amazing flowers held on tidy plants.
They are, of course, frost tender, and most varieties will need careful placement. In our inland towns they will need to be placed against a north-facing wall, preferably in full sun, and with well-drained soil. All varieties hate clay, and will not thrive at all in water-logged soils, so it pays to completely replace the soil if you are stuck with gardening on clay – or grow some of the smaller varieties in pots.
We have grown a couple of shrubby hibiscus for many years in containers. They are slightly neglected – they are never fed and seldom pruned – and I am sure we could do a let better if we spent a bit of time on them.
Firstly, we should be feeding them in spring/ early summer. Once established, Hibiscus are relatively hungry feeders, and will respond well to a good application of a general fertiliser. A slow-release form, designed for trees and shrubs, would be even better.
Hibiscus only flower on new wood (like roses, come to think of it) and a regeneration of branches each year is needed. Just prune back at the same time as you are pruning the roses in July/August, and they will respond with a flush of new growth that will bear flowers from December through to winter.
Hibiscus can cope with a very vigorous pruning. If they are starting to get a bit leggy and woody (they look very uninspiring when they do) just cut them back. Within a year they will have bounced back with a whole lot of new growth, and more crops of flowers.
Most varieties branch near to ground level and make attractively thick growth. If you have a mind to, they also can be trained to make wonderful espaliered shrubs.
A childhood neighbour grew a luscious pink Hibiscus against her chimney – it grew right up to the gutter of the house and threw large single flowers all summer long. I think the frost was probably training it, as I do not recall her ever trimming it.
The most common Hibiscus seen in New Zealand are the Fijian varieties. They are smaller growing, bushy shrubs, and are slightly hardier than their Hawaiian counterparts.
Perhaps the most common varieties are ‘Suva Queen’, with her double pink flowers, ‘Agnes Gault’, a single pink that was probably what my childhood neighbour grew, and ‘D J O’Brien’, semi-double tangerine.
Hawaii has a number of native species which have been crosses with the older forms to give a new race of plants. They are tenderer than the Fijian types, and need more sheltered growing conditions. This far south, they probably do best in a conservatory in all but the warmest sites.
‘Golden Belle’ has rich bright yellow flowers in abundance; ‘Hawaiian Sunset’ is cerise pink with yellow edges; and ‘Nathan Charles’ had large flowers of crimson red.
Some of the Hawaiian forms are not very vigorous on their own roots and thus need to be grafted.
The Fijian and Hawaiian varieties have been crossed and recrossed, and there are now literally hundreds of varieties around, many of them bred in New Zealand and Australia. It would pay to have