WHEN THE TALL bearded irises bloom, the gardener resolves on digging everything else up and pitching it out, to have room for more irises.

All other flowers I ever knew or heard of are self-limiting, but not the iris.

No gardener I ever heard of had enough irises, though he had enough daffodils, enough peonies, enough roses, enough lilies, plenty of daylilies and more than enough chrysanthemums.

That is because no other flower even rivals the iris for color, and twice as many irises produce five times the effect.

Daffodils gain nothing by large plantings, and peonies, wonderful though they are, have a narrow color range compared to the iris, and the effect of peonies is not enhanced by row upon row of them.

The iris gains enormously by being seen rank on rank. However small my planting of irises might be, I would at least contrive to see those few in ranks. So that if I had 100 feet of irises, I would have 10 rows of 10 feet each, rather than one row 100 feet long.

This does not mean the iris must be grown in rows like a vegetable, and the planting need not be solid with irises (though that is best), but it does mean there is no background so good for an iris clump as another clump of irises, and another one behind that.

If possible, I like to have them at least five deep.

Contrary to what the gardener may infer from some books, the iris is enormously appreciative of leaf mould. Wherever humus can be dug into a bed in fairly massive quantities, there the iris flourishes.

Recently we considered colors a bit, so here I should say simply that you can hardly have too many yellows of various tints.

As for culture, remember they like full sun, though they will make do with less, but until they are grown in the very best (sunniest, best-drained, richest) part of the garden without competition from other plants, it is hard to gain a correct idea of their splendor.

I have bent over backwards in the past warning gardeners of the shortcomings of the iris - the poor foliage much of the year (no matter what the books say about how find iris foliage is, it is very poor most of the time, and nothing to compare to peony or hosta leaves) and the hazard of iris borders, which eat out the insides of the rhizomes; and soft rot, which reduces everything to the very nadir of corruption. Also I have acknowledged the fleeting season of iris beauty - not more than three weeks of substantial color.

Worse than all that, the iris simply does not flourish (though it may manage grudgingly to give a lot of color) in a border of mixed things. The gardener need not hope to stick in a hollyhock here, a chrysanthemum there, a rose yonder, amid the irises. Almost everybody who grows irises sooner or later resigns himself to growing them alone.

This does not mean the whole garden must be nothing but irises (though one could fill it with worse) but simply that however large or small the iris area may be, it works better for there to be nothing in with the irises. Of course there may be peonies, roses, hollies or anything else you like behind the irises, but the iris commonly rots if other perennials encroach even slightly on its space.

Sometimes I feel I excuse the iris sins more than the iris sins are, and that is because it upsets me for people to find fault with the iris. I always feel like saying, "You have no right to grow it, if its trifling defects bother you."

Needless to say, it requires hand labor. Weed control does not work very well, in my experience, except by hand cultivation. I regret that - especially since the sunny rich site invites every weed of the western and eastern world - but I know no answer for it.

Many distinguished gardeners have given up and banned the garden iris altogether; and I must admit the iris is more work than roses, lilies, daffodils and daylilies put together.

Its flowers are more spectacular, of course, than all of those other things together. So life evens out.

Today (May 20) I have only a primrose-colored seedling, the medium-yellow 'Foxfire,' a white stitched with pink and a somewhat muddy blend ('Clairvoyance,' a nice enough flower but the colors are bronze and lavender and murkety-murk, and I have never comprehended why anyone would wish to grow such blends unless he had 400 or so clumps of pure colors - then a blend or two would be all right for the general hell of it).

My point is I have hardly any irises in bloom and, as far as that goes, I do not have many, in this small garden, even at their height of bloom.

But when they bloom, the world stops. Long enough for the gardener to get on. Really get on.

As for varieties, if one worse acquiring irises for the first time, nothing is better than the labeled collections of iris specialists; the cheapest collections (in a balanced color range) from the best sources is the way to go.

I would not buy irises from general nurseries. You pay too much. Iris specialists advertise, often small classified ads, in leading gardening magazines that can be consulted at libraries.

It has been more than 45 years now since I first saw 'Purissima,' the first great white garden iris.

And almost that long since we stood around the gaped at 'Alta California,' the first good tall yellow.

It is hard to believe there was a day we had no good whites, no good yellows, no good blues. Now we have superb varieties in those colors, and some of the very cheapest listed by iris growers are as good as an iris needs to be. Gone are the days when it cost a lot of money to acquire fine irises. In the 1920s and 1930s the new irises were $25 each, but were such astounding improvements over the old ones that you suffered a few years until the price came down to affordable levels.

Now there are still new irises, still improvements. But the improvements are extremely slight, and the cheap ones are for all practical purposes as good as the costly ones. The certainly did not used to be the case.

No picture I have ever seen captures the gaiety of the iris, and how incredible that virtually all its colors go well with each other. No flower except the lily is so fresh when it opens, and no other flower at all can produce flowers of such size in so many colors all at once, that can boast of flawless texture, unsurpassed elegance of outline, unrivaled dignity of carriage, unsurpassed profusion of bloom and - above all - quite unrivaled balance among virgor, delicacy and glory.

For this we pay a price. They do not sit there grinding it out all year like the floribunda roses; nor can they be left pretty much to their own devices, once planted, like the daffodil.

It comes down, no doubt, to the question whether the gardener wants the supremest wonder, even if for a little while, or whether he needs merely good design, good architecture, good taste - for very great gardens may be made without a single iris.

They are not, however, iris gardens, and are therefore defective.

I wish every gardener would try growing 10 rhizomes (roots) of 10 different irises in white, yellow, pink, lavender blue, deep violet, and gave them a fair chance. Then if they are too much bother to weed, or if they do not justify the space they occupy, why of course the gardener should replace them with plants that are better all-rounders than the diva iris. But I know many gardeners would succumb to the iris - with all her shortcomings - in a way they never dreamed possible for sane persons, if they just tried a few.

In many cases I believe, the kitchen or dining room (for in many houses these rooms just out beyond the main structure) could be demolished and a number of irises could be got into that space if it were sunny enough. It is also feasible (I increasingly believe) to level the house and move into the shed or the garage, opening up a good fixed space (often in the sunniest part of the lot) for the iris.

But I leave it to your own ingenuity and sense of fitness.