Search reveals varieties of kowhai

Press, 21 May 1982, Page 7

Search reveals varieties of kowhai

O\RDENER3] W DIARY

Derrick Rooney

To most New Zealanders, the kowhai is the national flower. However, I discovered recently when I started thinking about planting a kowhai and began looking around for a good form, very little information is available to gardeners on this most characteristic member of our flora.

Only three species are officially recognised in “The Flora of New Zealand” and these three are often muddled in nurseries. Yet most knowledgeable gardeners know that at least six probable species and numerous variations on them can be found in the wild. Even if you confined your search to Canterbury you would find at least five types that are different in size, in growth habit, and in time of flowering.

In the coastal hills of North Canterbury you can find kowhai trees that flower in June, two to three months before the main display begins; and in the harsher climate of the Rakaia gorge there are kowhais which flower in July. No attempt, as far as I know, has been made to bring these into cultivation, or to find out whether they will retain their early-flo’wering habit in gardens.

On Banks Peninsula I have seen some quite old-looking

plants, with mature crowns, no, more than 3m high on good soil; elsewhere there are some forms which, even in poor soils, reach two or three times that height. There is surely scope for selecting good garden plants from these smaller kowhais to match the reduced dimensions of many modern gardens. There is scope also for selecting forms which do not go through the persistent juvenile stage which can delay flowering for-as long as 15 years. . Only one such selection has arrived on the market in recent years—a bushy form of the common kowhai from Stephens Island, Wellington. This has apparently developed its low habits in response to the constant battering from the nor’west winds through Cook Strait. It looks as if it will grow larger in cultivation than the Im cited as its height on Stephens Island—my three-year-old plant is already pushing 60cm—but it is retaining the bushy habit, and its slightly drooping horizontal branches make it quite an elegant little shrub. It has not flowered yet. though it is said to do so at quite an early age (perhaps four or five years) and at intervals throughout the year, instead of in one great burst in spring. So far it has

been evergreen, unlike most kowhais, which drop their leaves in winter, or just before flowering. Apparently the Stephens Island plant is regarded by botanists as simply an aberrant form of the common kowhai (Sophora microphylla) which has responded to adverse conditions by altering its growth habit, both the bushiness and irregular flowering times being in response to the excessively windy climate of Stephens Island—the dwarfness enables it to withstand gales, and the irregular flowering perhaps improves , the chances of striking a period of good weather for pollination. But as it is obviously going to retain these habits in cultivation, gardeners are going to regard it as a separate species, rightly or wrongly.

In the horticuultural world the kowhai from north-west Nelson is already established as a species in its own right, even though it is referred by “The Flora” to the common -kowhai. This is Sophora longicarinata, or. according to “The Flora,” Sophora microphylla var. longicarinata. This tree is in some respects a better garden plant than the other larger kowhais, for its flowers, though paler, are larger, it is a small tree seldom more

than 4m high, and it has an elegant semi-weeping habit with very long leaves comprising as many as 40 pairs of leaflets. It does not go through the juvenile stage which causes plants of the common kowhai to look for many years like mounds of old wire’bulldozed out of a fenceline; and it flowers within seven years of raising from seed.

In the wild Sophora longicarinata is’restricted to the limestone hills of the Takaka district, but it does not need lime to grow well in the garden. Most of the trees in cultivation are believed to have originated from a plant cultivated by a Mr Treadwell, of Wellington, and at one time it was known as sophora Treadwellii. the recoginsed species of kowhai, apart from Sophora microphylla, are S. prostrata and S. tetraptera. Sophora prostrata is the bushy Canterbury and marlborough species which loves a dry climate and can be found in rocky places, often growing in association with the Marlborough daisies (Pachystegia) and the shrubby Senecio monroi, two other members of the garden elite in our flora. Botanists are not universally in agreement over the prostrate kowhai—some say it is merely a fixed juvenile

form of S. microphylla which has the capacity to flower and fruit. But it is remark-, ably uniform throughouut its range, and most people regard it as a good species. Despite its singular appearance, though, it is of limited use in the garden because it flowers sparingly, or in some years not at all— I spent a large part of. a recent afternoon in North Canterbury searching in vain for seed on plants of this kowhai. When it does flower the blossoms are inclined to be hidden inside the bush. Interestingly, their stems are twisted, so that they face upwards, unlike the other kowhais, whose flowers hang. Where it overlaps with the common kowhai the prostrate kowhai hybridises, and a range of . intermediate forms exist. Some of these combine the growth habit of the common kowhai with the dwarfness and orange flowers of the prostrate kowhai, and a determined search might well turn up some top-drawer garden plants. Sophora tetraptera, the North Island kowhai, is the largest of the New Zealand species and for that reason, perhaps, is less often seen than S. micropylla, though it is hardy despite its northern origins—wild plants do not

come much the Ruahine Ranges. Sometimes it is seen labelled “Sophora grandiflora” in nurseries and sometimes plants labelled “Sophora tetraptera” are hybrids with S. microphylla. Hybridism is rife in the New Zealand flora, both in the wild and in gardens.

The true North Island kowhai has leaflets three or four times the size of those of the common kowhai, and they are more-or-less oval, whereas those of the common kowhai are oblong.

The flowers of the North Island kowhai are larger, and often paler, and there are some very fine flowering forms, though here again little attempt has been made to seek out superior plants for propagation. I am lucky enough at present to have a seedling or two germinating from seed given to me by a distinguished gardener from a fine group of trees that he collected—as seed—at the head of the Moawhanga River. There is a dwarf form of this species which has been named, and. which is propagated from cuttings, though it breeds true from seed also. This is “Gnome,” a very slow-growing bush which may begin flowering when less than 30cm high. Plants in the Christchurch botanic Gardens which are more

than 40 years old are no more than 3m high. Little is known about the origin of this odd little kowhai. One story, unconfirmed, says that it originated in the long-defunct Buxton’s Nursery, in St Martins. Another is that it was a chance seedling which appeared in the Otari Native Plant Museum. Wellington, and it is sometimes known as “Otari Gnome.”