Versatile multi-layer garden

Press, 16 July 1982, Page 7

Versatile multi-layer garden

(®ARDENER'S!| DIARY ■

Derrick Rooney

» Last week, in the hope of illustrating the diversity of effect that can be achieved in a small area through the use of mini-shrubs and alpines, I described a few small rhododendrons; and a week earlier I discussed some other tiny shrubs with which they share — and create a framework for — a 6 sq m area of rock garden. Of course this framework, if it is to be interesting throughout the year, must be fleshed out with a succession of bulbs and herbaceous alpines — creating, if you like, a sort of multi-layer garden, with different plants coming and going throughout the year. These are plants which add real interest and diversity to a garden. Spring is as good a starting point as any for them, and one of the first to appear in spring is (was, rather; at present it is, unfortunately, a former occupant) the charming little Viola bertolonii. Most gardeners know the viola family only by the common heartsease (Viola tricolor), which can become a weed, or by Viola gracilis, the species from which garden violas were bred; but there are plenty of others worth growing, and Viola bertolonii is one of them.

It is a small, rich violet pansy with flaring eyebrows. It lived almost two years, flowered almost non-stop, resting only for a short time in July, and expired last autumn.

Numerous seedlings have come up. but most have hybridised with Viola gracilis or the heartsease, which pops up everywhere. The seedlings are in a range of colours and some of them are very good — a blue-and-white seedling which came up in the path is worth propagating from cuttings — but they are not Viola bertolonii. However, I leave most of them to flower, and Malthus's law ensures that the real thing will turn up again sooner or later. When it does I will be able to maintain it by taking cuttings, which is what I should have done in the first place. I thought an infusion of pink might produce something interesting, and tried to introduce Viola bosniaca to the group last summer (it flowers in a lovely, warm lilac pink), but my timing was bad — the newcomer died of drought, or heat, or both.

Another occupant of this bed, now reduced for the winter to small, resting rosettes, is Arabis ferdi-

nandi-coburgi. one of the few variegated plants which can be admitted comfortably to the rock garden — which is not, .on the whole, a place where variegated foliage looks right. Most people know variegated arabis only as the common edging plant that can be bought by the trayful during the planting season, but there are some aristocrats in the genus, and A. ferdinandi-coburgi is one of them.

In the wild, in Greece, it presumably has plain green leaves, but I have seen only the variegated form. Unlike most members of the brassica family, which tend to be free seeders, it has never set seed in my garden. It is tiny, ground-hugging, with smooth leaf-rosettes which are greyish green liberally streaked with white. In winter there are some reddish hues, too. Early in spring every rosette breaks out into masses of little white, cabbage flowers. Another good one is Arabis blepharophylla, a scree plant from California which is by no means easy to keep alive and healthy. The best forms of this have hot pink flowers, a refreshing change in a family dominated by white or muddy mauve. Also in this bed is one of the wulfenias — primula relatives from eastern and south-eastern Europe which have their flowers in spikes.

It was supposed to be Wulfenia carniblica, but the leaves are, too smooth and too lettuce-green; • presumably it is W. baldaccii, another eastern species. The flowers are small, densely packed in little spikes about Bcm long, light lavender blue.

In a good year they are charming, but like most members of the primula family they are allergic to heat and a few hot days about flowering time will make the flowers wilt.

The leaves, being very thick and leathery, stay green through the summer but do like a little shade, only a little — too much shade discourages flowering. I compromised by putting the plant on the south side of a rock, where it is open to the sky. Seve’ral true primulas are established in this bed. including the extraordinary Primula vialli, with its kni-phofia-like spikes of flowers which change colour from lavender to rosy purple as they age. giving the spike a two-toned look. Primula glaucescens was a misfire, but a Primula minima hybrid — like a tiny rosy pjink auricula — is increasing and Primula luteola, supposedly a moisture lover, has thrived on two dry summers.

Other members of the Primulaceae in this family are winter-flowering cyclamen, raised from seed under several different names, but all now. reduced to the one species, Cyclamen coum. They include the plants formerly known under the species names, orbiculare and atkinsii.

All flower through the frosts, in colours ranging from palest mauve-pink to intense rosy carmine. There is a pure white form, too, and I have sown seed of it a couple of times, but so far no white flowers have appeared. Both plain green and marbled leaves occur in this complex species. A common characteristic is the leaf shape, which is round, with the edges lightly tucked underneath, like mushrooms. Hidden away among these tiny cyclamen is the curious Polygonatum bookeri, a miniature Solomon's seal whose flowers appear almost at ground level and are pink. Its tall cousins, more familiar as border plants, almost without exception haye white or greenish flowers. The flowers of the tiny species face upwards, unlike those of its giant cousins, which dangle prettily .from the undersides of the arching stems, so that hookeri lacks the grace as well as the size. But it is worth growing as a curiosity. At present it is snugged

away below ground, but as soon as a few warmer weeks come the flowers will pop out, to be followed soon afterwards by the leaves.

Prolonged talk of the numerous plants in this small area of rock garden could become as boring as any list of names, but three prostrate sub-shrubs must be mentioned. These are Pemettya pentlandii, with blue berries. Pernettya tasmanica, and Myrtus nummularia.

•The former is said to be quite rare, which is hardly surprising if it behaves unto others as it behaves unto me. It is very slow growing, apt to die back, and reluctant to flower in our climate — but in those few seasons when it does well it is a treasure.

Pernettya tasmanica is reputedly a trifle frost-tender, but after almost six weeks of successive eight-degree frosts it is coming up laughing. It is tiny, with leaves only a few millimetres long, stays flat on the ground, and spreads by young shoots which push out just below the surface.

The growth is not aggressive, and is easily curbed by a couple of flicks with the trowel, so it is ideal rockgarden groundcover. So far mv plant has not flowered, but it is said to be very freeberrying once it gets started. As might be guessed, it comes from Australia. Myrtus nummularia comes from Chile, and should not be (as it sometimes is) confused with the “creeping mapou” of New Zealand, Myrsine nummularia. “Nummularia" merely means having leaves shaped like coins, and there are round-leaved “nummularias” in several rockgarden families. The round-leaved Chilean myrtle is a misfit in its genus, because it is tiny, and ground hugging, whereas most of the myrtles (New Zealand species included) grow into quite large shrubs. Myrtus nummularia clings to the ground as though handcuffed to it. In summer it has little creamy white flowers with big, brushy masses of stamens, and last summer there was a heavy crop. ' The pink, berry-like fruit are very pretty, but in spite of the numerous flowers only one was set. It hung on the bush for months, Ignored by the blackbirds, which were eating everything else in sight, until the frosts finally browned it off at the end of June.

At that stage I picked it, curious tb see whether it contained any seeds. It did; they were brown, and minute; and alas, I dropped them.