The iris has a rich offering for the garden

Press, 1 November 1979, Page 11

The iris has a rich offering for the garden

No genus has as much to offer in colour, fragrance, and variety of form as the iris family. To most people, perhaps the word “iris” is synonymous with the tall bearded group, often wrongly called “flags,” but the bearded irises are less than the tip of the iceberg.

There are hundreds of species, bearded and beardless, ranging from true desert plants from areas of Win rainfall or less to bog-loving giants that must have their, feet in standing water. Not all of them are gardenworthp, but many are; and some of these will be on display next week when the newly-formed species section of the New Zealand Iris Society puts on a special display at the annual iris and bonsai show in the Horticultural Hall, on Wednesday and Thursday.

Among the irises on display are likely to be the tiny Iris cristata and its even smaller variety, lacustris, from the United States, and Iris gracilipes, a very graceful woodlander from Japan — a trio of tiny treasures from the Evansia (crested iris) group. There may be. also, locally-grown displays of Siberian and Louisiana irises.

The latter, a polymorphic group originating in the swamps and bayous of the southern United States, has never attracted much publicity, mainly because they are of suspect hardiness in the colder temperate regions, including »Britain. But they are regarded as having a very bright future in New Zealand. Modern Louisiana irises have a colour range as wide as, if not wider than, that 'of the tall bearded irises, and they range from plants little more than knee high to giants of 7ft. Some have flowers as big as dinner plates. Only a few of the many varieties available are the products of controlled hybridisation; most of them were collected in the wild. Once dozens of species of Louisiana irises were recognised, but recent scientific work has resulted in a reduction to three or four “aggregate species” and a vast number of natural hybrids. One reason why they have never become very popular is that their requirements have not been understood, and they have a reputation of being difficult to grow. I must confess failure with my own efforts to date. In southern Louisiana and Florida they grow in rich, mucky swamps that are flooded in winter and spring, but dry out in late summer, at which time the plants begin a short period of dormancy. They do not, as many people believe, grow in standing water; though they will tolerate it while the weather is warm, water above the collar line is usually fatal in frostv weather. So the secret, the experts say, is to keep them wet but not flooded until mid-January or a little later; they can then be allowed to have a short dryish period. I am trying another selection of Louisianas this year, in a compost-rich mixture in an old pair of washtubs, sunk into the ground. They are in a part of the garden where, a large locust tree and a hedge suck out most of the moisture that arrives as rain, but with judicious use of the watering can I should be able to keep them pretty swampy as long as they need to be swampy. An advantage of growing them in “containers” in

this way is that it will help to curb their rhizome growth; when conditions are right their rhizomes elongate at a great rate, and they can swamp smaller neighbours and, if grown in a group, become inextricably entangled with one another. Several summer-flower-ing members of the “stylosa” group (I prefer this old name) may also be on display next week. The best-known member of this group is, of course, the winter-flowering Iris unguicularis, which comes from North Africa and southern Europe; but several desirable cousins are just coming into flower or bud.

These include the exquisite Iris minutoaurea, which has the smallest iris flowers of all; the Asiatic Iris ensata; and the rich violet-blue Iris setosa.

Iris setosa is a grand front-of-border plant for Canterbury gardens. It never grows more than a foot high, has neat foliage, and flowers very freely. The books describe it as a moisture lover, and I read a report recently in a copy of the R.H.S. journal of losses in summer drought; but in my garden

it does very nicely in a dry, sunny border. It was one of the few plants that never turned a hair during the big drought of 1977-78.

Iris ensata is yet tougher; it has long, sinewy roots that dig themselves vigorously into the soil. A bulldozer is of great assistance when an old clump has to be moved. Iris ensata has bluepurple flowers, rather like those of a Siberian iris. It is widespread in Asia, and is one of the most common plants in the really arid areas of China and Tibet. As far as I know no nursery in New Zealand lists this species at present, and on the odd occasion when it is catalogued the plant supplied very often is a variety of the Japanese Iris kaempferi, a moisture lover! But it is not difficult to raise from seed.

I have a clump coming into bud now from seed sown, the label tells me, in May, 1976. It will be in flower in a w'eek or two, and when the flowers open the stems will be about 18in high.

They should then make quite a pleasant group with a few drought-resis-tant shrubs among which 1 have placed them. There

are some pale yellows (provided by brooms and cistus), because I like the contrast of pale yellow against purple and mauve, but these will be gone soon, and most of the surrounding plants are in the same colour range as the irises.

I like to group colours that are close to each other, especially in the cooler shades, so that parts of the garden have a restful quality — complement, not contrast, is the theme. Next to Iris ensata is a bushy rosemary, which has been in flower for six weeks, the lovely “Jackman’s Blue” rue (kept bushy by an annual winter trim that also ensures continuity of supply throughout summer of its elegant blue-green foliage), and a blue-leaved juniper, “Pathfinder.”

The juniper has been a slow starter, but is now beginning to find its path upward, having doubled its size in the last year. Two other junipers make an understorey to this picture, and alongside them a miniature "jacob’s ladder” adds a smokey blue accent. It came from a Christchurch garden, and has no name, just “Polemonium species,” though it may a form of P. reptans. It is not much more than ankle high. Right in the middle of all this, and at the edge of the border, is a clump of the “Californian fuchsia,” Zauschneria californica. with softly hairy grey-green leaves. In high summer its brilliant vermilion trumpet flowers will positively vibrate out of this picture. By then the flowers of Iris ensata will be long gone, and seed will be ripening. I hope. Seed is the only way to multiply this species.

Unlike the bearded irises, it resents disturbance, and if a big clump is broken up with the help of an axe or a saw the plant is likely to express its disapproval by dying immediately or sulking for years.

Naturally, a species so widely distributed as Iris ensata has a variety of forms. Good ones have shapely flowers of superior size and substance, in a rich blue-purple; poor ones have untidy, dull bluish-grey flowers.’ I hope mine prove to be the former.

Iris ensata is one of the deciduous species, disappearing underground in winter but hanging on grimly to its dead foliage (even now the old leaves are hard to pull out).

It is always a late starter in the spring, but growth is rapid; the leaves of my plants have lengthened by 2ft in the last month.

GARDENER’S DIARY

I Bv

Derrick Rooney