N.Z. relatives of the rose

Press, 27 March 1986, Page 8

N.Z. relatives of the rose

Axrdener’s W DIARY

Derrick Rooney

The rose family is an enormous cosmopolitan one which includes the familiar garden flowers from which the whole group derives its name, a wide range of other ornamental shrubs, flowering herbs, and the fruiting and ornamental cherries, peaches, almonds, apricots, apples, plums, and pears.

Yet it is poorly represented in the indigenous flora of New Zealand. There is little of horticultural significance among native Rosaceae — the acaenas (bidybids), a few of which are excellent groundcover plants; a solitary creeping potentilla (whose status as a native is open to question); the bush lawyers, which are closely related to blackberries but less useful; and a handful of

geums. Geum is a big name in ornamental horticulture, thanks to a group of large-flowering perennials developed from the South American G.chiloense — long-flowering varieties such as “Dolly North” (soft orange), “Red Wings” and “Mrs Bradshaw” (bright red), and “Lady Stratheden” (yellow). The New Zealanders, alas, apart from a bright yellow species once found in North Canterbury and now presumed extinct, are a rather dowdy lot when placed alongside these exotics. An exception is the high-alpine G. uniflorum, which has large, glistening white flowers, but which when found wild is almost always in seepage areas, and demands a constant

supply of trickling water. I find it ungrowable. G. parviflorum and, slightly higher up, G. leiospermum are the common geums in Canterbury mountains. Both have small white flowers, barely large enough to cover a 5c piece, but their leaves can be quite attractive, especially in the forms with brownish or chocolate colouring. Geum pusilium, a tiny plant known only from the Old Man Range, in Central Otago, is worth growing, not for its flowers, which are minute, but for its attractive rosettes of dark green leaves.

In the wild it grows in damp, shady crevices, and this is the situation it

ought to have in the garden. Though it will survive quite dry conditions, it will not thrive unless it is damp. Geum pusilium may sometimes be obtained from nurseries specialising in alpine plants. As it is a rare plant it should never be collected from the wild.

Not many people would think about putting the fiercely armed bush lawyers in the garden, but

there are two worth cul-

tivating. Rubus parvus is a small, creeping plant with white flowers and raspberry red fruit which likes to sprawl on the ground, and may be accommodated in large shady rock gardens. Its hybrid, R. barkeri, has a similar habit, on a larger scale.

Collected near Lake Brunner near the end of the nineteenth century and thought then to be a new species, Rubus barkeri was subsequently identified as a hybrid with R. parvus as the pollen parent and the giant bush lawyer, R. cissoides, as seed parent. Similar plants have been found since, but they are rare. Two forms of Rubus

barkeri are in cultivation. One, collected within the last 20 years, flowers freely. The original plant flowers seldom, if at all, and is sterile.

My plant is the nonflowering form, but I don’t mind because it is for the leaves that I grow it. They are glossy, leathery in texture, and coloured bronze. In winter, rich purple tones develop. Rubus barkeri will grow happily in either sun or shade but the finest leaf colour develops on plants growing in full sun. Planted at the top of a sunny retaining wall, it will make a dense cushion, half a metre high and a metre or more wide.

Shade-grown plants will

also hug the ground if given no choice, but if one of its shoots finds its way to a nearby shrub it will soon work its way up to the top in the search for light.