YOU NEVER see the huge-leaf gunneras in Washington gardens, and I suspect the reason is that nobody ever got round to promoting them, least of all nurseries.

All the same, the gunnera is the largest-leaf plant that can be grown here, and with a bit of luck and skill, the plant makes a vast clump like a rhubarb only with leaves up to 9 feet in diameter on steps 8 to 10 feet high.

Of course, even if the plant were readily available -- it is not -- and even if it proved manageable -- and it is not always easy -- I think we would have to be content with smaller leaves than 9 feet.

I myself would settle for 7 feet.

G. manicata grows wild in southern Brazil, and you often see it in English gardens beside lakes or at the edge of bog gardens. The ones around the lake at Kew Gardens in London produce leaves about 4 feet across. a

But it depends a lot on how much trouble you take with it, and I suspect they take none at Kew. The directions given in William Robinson's great book, "The English Flower Garden" at the turn of the century urge the gardener to give it all the sun and all the water possible.

The hole in which the potted gunnera is planted should be 6 feet in diameter and 4 feet deep, with a layer of drainage stuff at the bottom and an almost endless quantity of rotted cow manure, leaf mould and loam.

As the plant emerges from the earth in spring, the leaves are packed in the crown and, before expanding, they look rather like green porcupines.

The plant is often called the prickly rhubarb. Both the stems and the back of the leaves along the veins are furnished with somewhat fleshy spines, not dangerous at all, but apparent enough.

On several occasions I have tried to raise gunneras from seed, without the least glimmer of success. Theoretically, you plant them in pots, keep them in the light and hope for signs of germination in July from seed planted in spring.

A couple of times I imported gunneras from England but never got them to survive more than a few weeks. I am not sure they like muggy summers, and they may possibly resent verticillium, fusarium and the other soil-borne organisms that flourish with us.

On the other hand, Hans Conard, in his books on water lilies about 1904, said he grew gunneras without any great trouble in Philadelphia, merely protecting the crowns with the plants own frost-bitten leaves in November.

When really flourishing, the plant makes a crown the size of a man's body. Accounts exist of a fellow mounted on horseback riding beneath one of these great leaves.

In the summer, when the wind blows gently, the great rough leaves rub together to make a gentle mysterious noise like a giant shaving, according to one writer who loves the sound.

The flowers are nothing to speak of; minute and packed together in a sort brownish red club.

I have been given a fine young gunnera plant, presumably for my modest virtues, and I do not propose planting it outdoors until settled weather in May.

The plant came, according to the little label on it, from Greer Nurseries at Eugene, Ore., and I guess Oregon is a little easier than England, though not much, probably.

I have dug a hole only 40 inches across and 20 inches deep, but shall of course complain bitterly if my gunnera leaves do not reach the same size as the ones mentioned in Robinson's book.

So often success -- I mean gorgeous spectacular success, such as none of us ever has -- depends merely on a lot of drudgery in preparation of the planting site, or special precautions in the way of shelter (a wall, a 10-inch mulch of cut honeysuckle branches in December, etc.) or unflagging duty about July 5 when one really does not feel much like Gunga Din but should be lugging water buckets all the same.

For gardeners who do not propose to spend several years acquiring and failing with gunneras, before ultimately achieving a fine figure of a plant 30 feet across, but who would like large leaves around a lily pool or bog, the ordinary rhubarb is handsome indeed. It does not need, or like, bogs, but may be planted in sight of the water, to give rather a tropical appearance.

Possibly the easiest test whether someone is ever going to make a gardener or not is to show the fellow a fine rhubarb plant. If he wants one, he is or else soon will be a gardener. If he does not, he will never be good for anything.