ONCE ON the Bayou Vermilion I noticed an iris with uncommonly small leaves and took a small piece of it home. It had been starved, and promptly began to grow all over the place in its new and lusher place.

It was merely the wild I. brevicaulis, with slightly grayed sky-blue flowers on its zigzag stalk. Antoher time I spotted a tiny iris with leaves only two inches high and brought it back, wondering what in the world it could be. It too began to grow like a weed and turned into the 4-foot-high Iris giganticoerulea, with electric deep gentian-blue flowers.

On a third occasion I noticed an iris in a damp meadow beside an Arkansas road.

I was the terra-colored Iris fulva, but I had not expected to see it growing where I in fact found it.

All three are so-called "Louisiana irises" and by crossing the three species back and forth a great assortment of colors-blues, pinks, yellows, blends-are now to be found.

For several years I was amazed at the beauty of these wild irises, and I still think the flowers as lovely as anything in the vegetable kingdom, but they have a lot of faults as a garden plant.

The rootstocks run about, for one thing, and you do not get as many flowers per square yard as you do from many other irises. For another thing, the stalks often lean about instead of standing up straight and, worst of all, the foliage is not very good in many of them.

They start blooming towards the end of the tall bearded-iris season and bridge the interval before the Japanese irises start.

At first I erred in giving them what I thought was a replica of their natural conditions, that is, lots of water in spring, hard baking in summer and dry in the fall.

But later it struck me they did better in ordinary-ordinary, my eye-rich sunny beds with plenty of humus. Although you may see them baked like a rock along the top of bayou banks, I think that is only because they seeded there and have no way of moving off. They certainly do not object to high life if they can find it.

I now think those irises are not so well worth space as many others, but they are admittedly glorious in flower.

I notice that the one I miss most, from my former garden, is the plain I. fulva, a muted red-tawny flower about the size of a lemon slice or a bit larger.

It is always conceivable that a gardener will have a low place, say a foot or two longer than the surrounding ground, in full sun. I had such a spot where a stone terrace drained. I had tried various things there, but nothing was really happy until I planted Iris fulva, and it was in heaven.

Admittedly, the fine sheaves of thin sword leaves flopped in the summer, but they were vigorous and straight in the spring, and nobody's perfect.

These wild creatures are sold by iris specialists especially in Louisiana and there are ads in garden magazines.

I was checking to see how my pal-metto came through the winter (alive and outraged) and something about the low area a couple of feet distant made me think of the wild red iris. Maybe I will never grow it again, maybe I will.

Garden plants are interesting, in that so many of them almost obsess you at one point in you life, and then you let them go without any special pangs.

Except that once in a great while you see something that reminds you forcibly of the time you grew them and the memory becomes surprisingly intense.

Some gardeners are surprised to discover the wild Louisiana irises are hardy in New England. Even in England, where they have no sun and no heat, many of the Louisianas can be grown-and they bloom there, although somewhat grudginly.

Near the Gulf of Mexico people grow them madly.

Up here I suspect they will appreciate full sun, though they do not require it in the Deep South, and up here I would give them the sort of good soil you would give roses and other garden irises, and although it does not require water standing over it from time to time, I. fulva would probably appreciate it.

Its color is unique among all the flowers I know, and curious gardeners will probably fall for it. It is nothing like as showy as the average tall bearded or German iris, but when it is in bloom in late May, the gardener will not think of that.