A bush like rusty netting

Press, 2 March 1984, Page 13

A bush like rusty netting

GARDENER’S 3 DIARY

Derrick Rooney

To most gardeners, the helichrysums are well known as the brightly coloured annual “everlasting flowers” from Australia, and the smaller, silverleafed, and equally brightlycoloured alpine species from South Africa. New Zealand’s contribution to this widespread genus is a couple of whiteflowered grassland daisies and a group of the most odd shrubs imaginable. One of the latter, Helichrysum dimoorphum, was in flower in my garden last week. Its sprinkling of scruffy, off-white blooms was a big event — not for their beauty (they have none) but because the plant is not only singularly odd, but one of the rarest in our flora. It is a scrambling, climbing, or prostrate bush which grows wild only in the Lower Waimakariri Basin. “Dimorph am" means “taking two forms,” and is a description well applied. Grown in the open, where it will tolerate short commons and somewhat parched conditions, this plant makes a rugged, divaricating little bush which for most of the year looks like a roll of rusty sheep netting which has been run over by a truck. To be sure that it is alive you have to feel it; you can actually detect by touch the difference between a living plant and a dead or moribund one. I can’t actually say what the difference is — it’s just a sensation that flows back through the fingertips. There isn’t anything magic about it. Only at the very bottom of the plant, in the shade of the hard, wiry upper shoots, is it possible to find conventional leaves on an opengrown Helichrysum dimorphum. If the plant is grown in shade and allowed to climb over another shrub, from the shady side, its stems are quite leafy until they reach and spread out over the sunny side, upon which they\ assume once again the rusty-wire look. Grown in the open, in the gritty soil that it loves, it will make a dense mound, halfway to knee height and a metre across at maturity. Grown as a climber, it will go up to two or three metres or more to reach the sun. The flowers are small, raggedy, off-white, and have no petals. Fortunately, this heli-

chrysum is well established in cultivation, so there is no need for anyone to disturb the few hundred plants which comprise the remaining wild populations. It will grow in gardens from cuttings or seed, which usually comes true, even from garden plants, though the other New Zealand species, when grown together, cross like fleas in a straw mattress. Natural hybridism is one of the things about New Zealand plants that help to drive gardeners — and, one imagines, taxonomists — dotty. Hybridism is rife among several groups, and helichrysums are among the worst offenders. An ecologically-minded friend tells me this is a sign that we have vigorous and still actively evolving flora, but this crumb of knowledge is slim compensation for the gardener grappling with the complex taxonomy of the mountain daisy bushes. To make matters worse, several of the familiar names have been changed. H.n« *, - hybridise among themselves they cross out with some w? and, I believe, with the New d“ ITS’ XE One of the most attractive native alpines to become available in recent years is a result of a chance cross in the wild between Helichrysum depressum, a Can-terbury-Marlborough shrub which looks like a heap of oxidised wire offeuts, and Raoulia glabra, one of the green scabweeds. The result of this mixed marriage is a little, slowly spreading shrub with knobby upright branches

only a centimetre or two high, and narrow, ashengrey leaves. It thrives in the rock garden in gritty soil, in a cool aspect, where it can get its roots underneath a paving slab or a large boulder. Helichrysum depressum also hybridises with H. parvifolium (formerly microphyllum), a greyish-green whipcord species, and some of these hybrids are, surprisingly, in view of their parentage, so silver as to be almost white. A particularly good one, found originally, I believe, on Mount Tapuaenukau at the head of the Awatere, is in cultivation, though it is still rare. Helichrysum depressum itself is an intriguingly bitter and twisted little bush, but its prospects in horticulture are handicapped by propagation difficulties. A friend who is a professional propagator tells me that in seven years trying he has not succeeded in rooting cuttings of this species. All the others, and the hybrids, T B r^’XiT a! they are mostly plants which favour dry, exposed habits in the mountains, they are p rone t 0 ro t j n an over - humid atmosphere - The secret of propagating them seems to lie in striking a balance, so that the propagating medium is kept just moist enough to keep them alive, but not so moist that they collapse. My experience with them has been that they root best in the cooler months, so that the time to take cuttings is > a u te autumn or early spring, The y cannot be hurried, rooting may take months. * haven t grown Heli-

pact variety, tumidum, from the Otago Peninsula (this is the form most frequently offered in nurseries); a knobby one from southern Marlborough which may be a hybrid with the remarkable “coral plant,” H. coralloides; and an erect form from Lake Tennyson with plenty of white tomentum on its stems (variety tomentosum, I am told). Helichrysum coralloides, mentioned above, is a Marlborough plant, and a well named one — old battlescarred bushes in those harsh mountains do look as contorted and ancient as a coral reef. Plants are sometimes available from specialised alpine nurseries, though this daisy is not nearly as easy to establish in lowland gardens as the others. I finally have one away now, I think, after years of trying; it even flowered this year, though that event did not produce any sight worth writing home about. The fat shoots, wholly or partly covered with white tomentum, are what this plant is all about, and if you want a weirdo shrub that your knowledgeable visitors will admire you could choose this. It needs full sun, cool aspect, gritty soil, sharp drainage, and an abundance of water in summer. Less rugged, but prettier and a lot easier to establish, is Helichrysum plumeum, which comes from mountains in South Canterbury. It is another whipcord, but its thin stems are densely covered with long, yellowwhite wool. It quickly makes an irregular, spiky little bush and takes years to outgrow its welcome in the rock garden.

chrysum parvifolium, though I do have a plant of the hybrid which is beginning to make a picturesque little silver bush. Near it, and making a silver carpet rather than a bush, is a little plant which has been identified by the D.S.I.R. as a cross between a grasslands daisy, Helichrysum filicaulis, and the conventionally shrubby H. aggregatum. This was grown from cuttings off a plant found by a friend in the Lees Valley, but similar plants have been found in other localities. One of them was sold last year by a Southland nursery under the label “Helichrysum selago X bellidioides.” Wrong both times. Helichrysum selago is the name by which both gardeners and trampers are familiar with a little whipcord shrub that grows in rocky places, outcrops, and crevices throughout the mountains of the South Island. Recently, after the discovery that the “type specimen” (the one on which the description of the species is based) in the D.S.I.R. herbarium is a hybrid plant, doubt has been cast on the validity of this name, and it now seems likely that what was thought of as a large, widespread and variable species 1 is actually a complex group 1 of natural hybrids. Heli- 1 chrysum intermedium, formerly a variety of H. j selago, thus becomes the > “true” species. No wonder ' gardeners get confused. J I have half a dozen of 1 these forms in my rock 1 garden, from various parts 1 of the South Island from ’ southern Marlborough down 1 to western Central Otago. 1 All are different. Among * them I like best the com- 1