RECENTLY I mentioned, with a hint of reproach, that the waterlilies at Longwood were rather sad looking when I saw them, but maybe the weather had been all wrong in the few days before.

The people at Longwood, the duPont estate at Kenneth Square, Pa., feel they have one of the finest displays of waterlilies in America; and it turns out they are quite fond of the huge "Victorias," and perhaps spend much energy on them.

This year the gardens, open to the public, have eight of the hardy waterlilies; and I suppose there was a similar paltry assortment when I saw them. There is nothing wrong with not growing hardy waterlilies, but of course I was severely disappointed at the Longwood collection of only eight. Many a town gardener grows that many.

The ones they have this year are "Attraction," "Comanche," "Helvola," "Joanne Pring," "Paul Harriot," "Poestlingburg," "Rose Arey" and "Sunrise," all of them standard sorts and nothing wrong with them.

God only knows what the fountain basins of Longwood cost, to build and to operate; and if you walk up close to them, they are extremely ugly with the plumbing showing; but that is not important, since the ordinary visitor gawks at anything that obviously cost a lot of money.

But it would have made more sense, if the duPonts had liked waterlilies as well as geysers, to take a fraction of the money and build pools for a nice assortment of, say, 100 of the best hardy waterlilies.

At large gardens, it would be nice to see enough of them to form an idea of their range.

Of course, you can't grow everything. But if you rather preen yourself on having one of the finest waterlily displays in America, I would think special effort and judgment would be a good thing; and I would not myself want to present the public with eight little tubs of the hardies.

Now when it comes to tropical waterlilies, they do well; and it was probably some accident of weather that they did not look like anything when I saw them.

They grow several night-bloomers, the ones that open towards dark, or after dark, and close the next morning. The Longwood assortment consists of "Antares," "Emily Grant Hutchings," "H.C. Haarstick," "James Gurney," "Missouri," "Mrs. George C. Hitchcock," "Juno" and "Red Flare."

Of these - not to split hairs - "Juno" and "Emily Grant Hutchings' are the best.

The greatest show comes from the day-blooming tropicals.

I give them extra points for growing Nymphaea coerulea, the blue Egyptian lotus, which is easily grown for seed, but which I have not noticed in recent years on the lists of waterlily dealers. It is an elegant flower, but has the serious fault of closing about noon.

Longwood does not grow "Blue Beauty" or "Pennsylvania" (synonyms), which is a seedling of the blue Eyptian and reckoned the finest blue day-bloomer.

Also missing this year is "Mrs. Edwards Whitaker," a very pale blue a foot or so in diameter. It does not bloom as freely, usually, as some of the other blues, but it is very lovely.

They have one of the most engaging of all small waterlilies, "Daubenyana."

This has flowers often no larger than a dollar of light blue, often rather washed-out. But its leaves are no larger than your hand, and each leaf, starting in mid-July, produces a tiny plant in the center of the leaf. These may be detached and grown in small pots; and even if they are left sprouting on the parent leaves, they commonly produce tiny flowers.

It was produced at the Oxford Botanic Garden around the turn of the century.

The wild N. capensis azurea is at Longwood, and so are two other treasures, N. gigantea and its variety Hudsoniana.

These are often not listed by dealers. Sometimes the gardener, if he writes in December or January, can get the great establishments like Triker's (dean of commercial aquatic dealers) to grow a few. I have seen this waterlily flourishing outdoors in Connecticut (planted out in mid-June) with a fellow who does not know it is difficult.

Its great fault is that it likes more heat than we can rely on here in the East in June.

Other day-blooming tropicals at Longwood this summer are "Albert Greenburg," "American Beauty," "Aquarius," "Aviator Pring" - a particularly nice yellow, if I may say so - "Bagdad," "Bob Trickett" and "Director George T. Moore."

"Bagdad" and "Director Moore" are particularly free-blooming, by the way (both blue), and "Bagdad" has a reassuring full plump look. "Director Moore" I have grown in both a horse trough and a garden pool, and it has the merit of producing relatively small leaves; its color approaches navy blue. It blooms its head off, and may be considered superlatively fine. The only trouble with it, as far as I am concerned, is that I like other blues better, though I liked it well enough when I grew it.

"Bob Trickett" has the reputation of growing easily (they all do, if satisfied with their pool, but "Bob" has the reputation of behaving quite well in chilly rainstorms in June).

"Eldorado," "Enchantment," "Evelyn Randig," "General Pershing" - could we pause a second for the general. This is a pink, with a bluish suffusion. It opens its blooms early and keeps them open longer than most. To omit it from a collection would be as unthinkable as leaving out "Pennsylvania" or "Mrs. Whitaker."

"Green Smoke" (now there's an unusual color, a pale flower suffused green; rather ugly to my mind but certainly interesting), "Isabelle Pring," "Joe Cutak," "Judge Hitchcock" (another blue with a dandy disposition for amateur pool owners), "Midnight" (very dark, violet blue, and I notice many do not really care for it), and "Mrs. George H. Pring," the oldest of garden whites.

"Castaliflora," another pink with a bit of lavender in it, and quite pretty but by no means the equal of "General Pershing" as I see it; N. colorata, a wild one with lavender flowers decidely small and not many petals, but a charmer, and blessed with neat tidy leaves that grow evenly in a rosette, very good for pools 4 or 5 feet in diameter.

"Pamela," "Panama-Pacific," "Peach Blow" (all these are lovely, needless to say, and this one certainly is), "Persian Lilac," "Pink Platter" (one of the finest with huge flowers), "Red Beauty," "Rio Rita" (which adapts nicely to smallish pools), "Shell Pink," "St. Louis," "St. Louis Gold" (also said to be good for small pools; deeper color than "St. Louis," which is itself very fine for large pools), and finally "Yellow Dazzler."

The great water platter, Euryale ferox, is rare in gardens, mainly because of its enormous leaves.

They are smaller than those of the "Victorias," however, which have leaves up to 7 feet in diameter. I think Perry Slocum in Florida grew one of the Longwood hybrid "Victorias' with leaves 8 feet in diameter.

This wonderful (but hardly for gardens) plant grows in the Amazon. Its flowers are more than a foot in diameter, washed-out rosy lavender, and you should have a pool 20 by 20 feet to grow one plant of it.

You can grow it in a tub, if you're determined, but then the leaves will be tiny.

About 30 years ago I leaned over to build up a bloom for a photographer and got my tie in the water, a brand new one, and never could wear it afterwards. This caused me not to like "Victorias."

The plant first flowered (as far as gardeners are concerned) for the duke of Devonshire in 1849 and was named for Queen Victoria, who was presented a bloom.

In London, gardeners should always trot out to Kew to see the delightful glass-house built to grow this "Victoria."

V. amazonica was formerly called V. regia. There is another one, very similar, called V. cruziana. The two species may be crossed, as in the Longwood hybrids. The one usually grown in lily pools outdoors is V. cruziana, partly because it is supposed to be a bit hardier and partly because its leaves are not quite so vast as the other.Also its turned-up margin is a bit deeper, and some prefer it.

If you cut a piece of plywood or stiff cardboard the size of one of the vast leaves and set it on top, you can stand a beautiful girl on it or, for that matter, a plain girl. Or even two, or maybe even three, since the leaf will support up to 300 pounds. CAPTION: Picture 1, At Longwood Gardens, the leaves of the "Victoria" waterlily are so big and buoyant that Stephanie Clouser and Heather Bemis, daughters of Longwood employees, can stand on one. Courtesy Longwood Gardens; Picture 2, Longwood's assortment of waterlilies includes both big and small varieties. Longwood Gardens photo