From its root to its flower, the iris is the most unexpected of plants. No doubt it is an ''interdependent system''. But it hardly looks like one. Who, not knowing, would guess that out of that neat and pointed bud such an opulent and dressy bloom will unfurl, throwing back its brown papery wrapping like an opened present? There it is, almost outrageously, an extrovert rarity with its three distinctive downward curves (aptly named the ''falls'') and its three answering upward curves -- the ''standards'' -- as unlikely as you like, this exotic flourish of colour and ebullient form.
Just as unimaginable is the elegantly tall, branching stem appearing out of the knife-blade leaves which fan from the base like a hand of cards.
This iris stem is an obliging rather than an inevitable arrival. You never quite know where, or even whether, it is likely to shoot. But when it does, it echoes in miniature a lift-off -- a passage from earth-bound to air-borne, from sod to sky.
And there at its foot is the old elephant-wrinkled rhyzome, the gnarled fist which holds the splayed leaves. What could possibly look less consistent with the marvel and grace of growth above it, than this crusty root tuber, half out of the soil? It is infinitely less promising as a form from which iris beauty springs, than ever the cygnet was a doubtful precursor of the swan.
A swan among flowers the iris is, with something of that bird's regal posture , a fact which did not escape the attention of medieval emblazoners. It was reputedly a king, but more likely a designer of heraldic devices, who elevated it from common ''flag'' to royal ''fleur-de-lys.'' The iris was also tempting to mystics in search of numerological symbols: its three-of-everything was a gift to them.
The iris is fascinating to botanists. It is irresistible to insects. And it is a positive field day for hybridizing humans. The last are to be praised for widely extending its colour harmonies, making it truer than ever to its Greek name meaning ''rainbow'', so that today's irises can be inky-black or paper-white, flamingo-pink or chocolate-brown, lucid butter-yellow or the ethereal blue of a shadow on snow. Their colours can be strange, almost sinister. They can be purity itself. It is in the range and extent of their violets and purples, however, that they are finest. It was for this colour that van Gogh painted them: violet, the antithesis of the sun's fierce yellow.
That he might never have painted an iris is a dull thought. But he did indeed pay his vigorous tribute to the flower on a number of occasions, and that universal style he evolved, with its outline and energetic dash of oil paint, adapted marvelously to the subject. This painter made his brush strokes move in the direction of the objects he painted.
A chair, a pair of boots, a bird's nest, or a dense patch of garden irises, all have the same intensity of vision, the same emphatic zest for colour and shape. It was the violet of the iris's flowers and the light blue-green of the leaves and stems which van Gogh always noted in his letters. Flower colour played a more than significant role in the development of his richly inventive palette, but the form of irises clearly interested him acutely as well: the paintings make this clear.
It happened that the first and almost the last paintings made by van Gogh during his one-year stay at the asylum in Saint-Remy were of irises, probably because it was May on both occasions. The picture on today's page is the first painting. On neither occasion was the flower treated as a receptacle for anguish. This is a wonderfully positive and undisturbed painting; it reflects the pleasure the garden gave him at the twelfth-century monastery where he stayed.
The way he has re-created the essence of these plants in paint is typical of his genius for comprehending and celebrating complex natural forms with apparent simplicity of means. The lessons of Japanese art have not been forgotten: Hiroshige made a print of growing irises to represent summer. Van Gogh had studied Japanese prints closely enough to make copies of several. Now, painting irises in the Saint-Remy garden, the Japanese love of these flowers, as well as a living respect for their very growth as a subject for painting, emerged in van Gogh's art with a new force. These were not cut flowers in a vase, in the Dutch tradition. Nor were they drawn as botanical specimens. They were a concentrated mass of rooted plants in close-up. Van Gogh describes with determination their slender spathes, awkwardly angled and almost overwhelmed by the size of the blooms they support; the crowded extravagance of this flowering; the leaves twisting up like green tongues of flame -- all displaying the alchemy that can occur when a great artist happens to come in intimate contact with a great flower.