Small irises give a bright display in pots or rockery

Press, 18 February 1983, Page 14

Small irises give a bright display in pots or rockery

A thought that struck me the other day while I was cleaning and repotting some bulbs is that some of the most rewarding and colourful plants to be grown in pots for spring display may be found among the small irises. The name “iris” for most gardeners summons a picture of the familiar, multicoloured bearded sorts, but there are, among the small, non-bearded irises, a number of species which are wonderful providers of early colour in the rock garden — or in pots. These are the bulbous species ■of the reticulata group. A dozen or more species have been named, but the four most likely to appear in nursery catalogues are also the easiest and best for general garden' use and for growing in pots: li. histrio, histrioides, danfordiae, and reticulata. Selected name forms of all these are available from time tp time, and hybrids also occur. Another which is sometimes listed — but almost always turns out to be the hybrid “Clairette” — is Iris bakerana. This is a miniature of reticulata which in recent

years has had its status reduced to that of subspecies of reticulata. The differences between the two are very clear to the horticulturist, regardless of what the taxonomists say. Bakerana is tiny, spidery but very neat; has distinctive bitone flowers, and has eight ribs on the leaves. Reticulata, also spidery, is bigger and has four-ribbed leaves. So far, bakerana has eluded me; I have bought bulbs of that name several times, and been given it once or twice, but always the bulbs have turned out to be "Clairette.” ; It is not always the fault of the grower when this happens, because it is very easy to get two very similar bulbs muddled. Sometimes customers wander along nursery rows, pull out labels to read them, and put them back in the wrong places. But it is infuriating. A prime example was my experience a couple of years ago when I was delighted to obtain from a Tauranga mail-order nursery a couple of bulbs of rare autumnflowering Leucojum roseum, a tiny pink wisp of a snowflake. I should have been suspicious when the bulbs mulLtiplied so rapidly that after a

Gardener’s W DIARY

Derrick Rooney

year I had half a dozen to give away to friends, but I naively went on thinking I had had extraordinary good fortune with a rarity — until the bulbs flowered for me in their second autumn. They were the common white autumn snowflake, listed in the same catalogue at a third of the price I paid. So it is with Iris bakerana. The history of this bulb in commerce is a trail of broken promises and erroneous labels. I'm just happy that I have now lined up a reliable local nurseryman who has an imported stock of the l real thing, and has promised to save his first spares for me. I suppose “Clairette” got in first because it is much more satisfactory as a garden plant, it is easier to grow bakerana, and it increases rapidly, whereas bakerana is slow to multiply; it does not form bulblets at the base like the other species but relies on division of the old bulbs. I like “Clairette”; it’s good value. But it has come down to the principle of the thing. I want bakerana, and I won’t be satisfied until I have it, and if I do get a stock it will have to be from a commer-

cial source, because even if I could afford to fly halfway round the world there is no chance, as things stand, of picking up a few bulbs from the wild; Iris bakerana grows in the mountainous areas along the Iran-Iraq border, and beautiful though it is, it is not worth being shot for. Iris reticulata also grows in Iran and Iraq, but extends north to Turkey and east into the Caucasus. Photographs of the bulbs growing in their habitats indicate that this is a species variable in size and colour, and in fact the common form in cultivation (a deep violet purple) has been recorded only once in the wild in recent times — in northeastern Iran by the late Paul Furse. ' Iris reticulata has a wide altitudinal range, from hilly country close to sea level up to 3000 metres. The leaves are very short at flowering time but shoot up quickly afterwards, only to die down abruptly in early summer. The common cultiv-

ated form multiplies at a rapid rate, flowers in the cool parts of the garden just as early as it does in the hot spots, and sets plenty of buds, even in a cool summer.

It must have a dry spell in summer, but does not need the “baking” (prolonged exposure to high soil temperatures) that some other Middle Eastern bulbs demand if they are to flower.

Like the other cultivated species, Iris reticulata is impervious to any frosts that the New Zealand climate can throw at it.

Though not the first to flower it is usually the first of the spring irises to appear above ground, and its hoarytipped leaves sometimes push through the hard ground in mid-autumn, though they make no significant growth until spring. Several good named forms are available, including “Cantab” (raised by the late E. A. Bowles), light blue; greenish spotting in the eye. Plants are readily identified by this colour combination, and by the tiny standards, which are reduced to mere bristles between the falls. It is a Turkish species.

Iris histrio and I. histrioides, both also Turkish, are often confused. They are

“J.S.Dijt,” reddish purple: and “Joyce,” deep lavender with paler standards. But for outdoor display the old commercial form is best. For growing in pots “Clairette,” though it is only half reticulata (the other half is bakerana), is unbeatable.

Iris danfordiae is a much-sought-after species, but not many gardeners grow it well because it has a sad tendency to impermanence; the fat, healthy-looking bulbs that you buy usually split up, after flowering, into masses of tiny bulblets that take years to regain flowering size (if they survive so long) and in the meantime are vulnerable to damage by the trowel or the hoe. Once planted in a sunny rock-garden pocket where it can remain dry, warm, and undisturbed in the summer, this bulb should be left alone. Eventually it will make a clump big enough to include a few flowering-size bulbs every year. , It is worth a bit of effort, because it is one of the prettiest of the small bulbous irises. The flowers are deep yellow, an unusual colour in this group, and have an orange crest on the falls and

about the same size, and superficially similar. Both have larger, and more substantial flowers than reticulata, and histrioides is a little larger than histrio. The latter is often the first of the group to flower, and probably the most weather resistant. The colour is usually pale blue, though there may be darker spotting on the falls, and the leaves are well developed at flowering time — a significant point. Histrioides flowers from the bare ground, and the leaves do not appear until the flowers have faded. The colour is intense blue, and the falls spread almost horizontally. Several named forms and varieties are available, and there are hybrids with reticlata, which sometimes make identification difficult. The flowers of Iris histrioides may be badly marked by rain but are seldom, or never, damaged by frosts, and will happily poke through snow — in the wild all these species flower near the snowline. A number of other species in this group occur in Asia Minor and Central Asia, and all are highly attractive if photographs are to be believed, but they are rare both in the wild and in cultivation, and expensive if you can get them. The creme de la creme is Iris winogradowii, a treasure which occurs wild only in a small region near Tbilisi, in the Georgian Soviet Republic. I saw this in flower last year in . a Mid-Canterbury garden whose owner, a skilled grower, had imported and acclimatised a bulb. The flowers are larger than those of histrioides, of a more rounded shape, and have more substance. The ground colour is a smoky lemon yellow, and there is an orange crest. This a very rare plant both in the wild and in cultivation. Seedlings take a long time to reach flowering size, and mature bulbs do not, or so I’m told, produce many offsets. As far as I know it has never been listed by a New Zealand nursery. If it is you may have to sell the car and mortgage the house to buy it.