HOW GLORIOUS the hot weeks have been for our tropical visitors -- the petunias, zinnias, marigolds, lantanas, verbenas and so on.

But most of all I think the progress of the moonflower has pleased me most. Roger Pineau gave me some seeds which I started in pots but did not get planted in the open ground until early July.

Really the seeds should be started in pots indoors in late April and planted out the end of May.

The moonflower since 1773 has been a summer treasure of Western gardens. Its name, Calonyctin aculeatum, refers to its beauty at night and its little bumps on the stem. It is like a very large morning glory -- 6 inches across -- only it is less trumpet-shaped than most morning glories. The moonflower blooms are flat like a tray, dazzling white, and they open about 9:30 at night, closing the next morning, sometimes as late as noon.

It is found in the tropics of both old and new worlds, and I do not know its original home.

The flowers are strongly scented, a trifle sickly in character. They are like thin strong silk, so white they appear to be illuminated, even on a fairly dark night. They do not care much for moderate balmy weather, but if it gets really hot, the sort of weather corn grows in, these vines spurt into growth, sometimes far exceeding the 10 feet that is given as their ultimate height.

They love full sun, or as much as they can get, and plenty of water and fertilizer. I try to keep a circle a couple of feet in diameter clean around the stem of the vine. If this dirt is lightly scratched with a trowel (an inch or so deep) after it begins to dry (say the day following a watering) and if the vine is given maybe five gallons of water two or three times a week, and if a scant handful of fertilizer is dug in once every 10 days or so, the vine will soon come into its own.

It has to reach a god size, 8 feet or so, before it begins to bloom well. It twines and is very happy on tall chainlink fences around factories. If grown on a sunny wall, it needs wires or netting to twine on. Once it gets going, side shoots emerge and a dense fountain-canopy effect is produced.

You can tell in the afternoon which buds will open that night.

In Tennessee-Mississippi, and I suppose everywhere else, it was the custom to keep an eye on the moon vine and when 60 or so buds showed they would open that night, to ask people over to watch them.

Unfortunately, people in that country talk so much that I cannot recall seeing the buds open very often. They tremble and vibrate when they open. Usually someone would say, "the flowers are out," and everyone would run over to admire them, then back to jabbering.

Equally festive is the night-blooming cereus. In our neighborhood there lived an old cereus in a tub. It was 97 years old, the last time I saw it, and produced 120 flowers open at once.

When it bloomed (and you can tell by late afternoon which buds will open) its proud owner would phone round the neighbors and there would be punch or champagne (rather dangerous in hot weather with people sitting for some hours) and cucumber sandwiches for refined persons, and ham and potato salad for mere mortals.

These parties, once such a feature of the American summer, were always spontaneous, since you had only a few hours to plan them and invite people. It was always astonishing to see how many people could come at the last minute.

The only other night-blooming flower I miss up here is the night jasmine, which grows perfectly in Washington, but you rarely see it for sale in late spring, which is when you plant it.

It has pointed leaves about the size of your middle finger ranged along arching stems that may be 6 feet long. In August it truly hits its stride and as the oppressive breathless days come when the trees all look a bit tired, the night jasmine sits in its well-watered spot, or in its great oak tubs, and vast panicles the size of phlox or hydrangeas begin to open their florets.

These are greenish-yellowish-white, long tubes not much thicker than the lead of a pencil, and the individual flowers are no wider than a tomato seed. They are noting at all to enchant the eye.

But about 9 o'clock they send out waves of the most intense scent I know in a flower. It is vanilla and clove mixed and it is detectable for maybe 20, maybe 50 feet.

Sometimes these flowers were cut and mixed in with zinnias or other summer flowers on a dining table. All went well until about halfway through dinner (for they do not send out their waves of fragrance till it's good and dark) then wham, no flavor at all could be tasted; everything was dominated by the night jasmine.

People in my country used to plant them where the scent could be managed:

You would plant them outside a south window. The fragrance would find its way into the house on the summer air. If it was too strong, you closed the window.

This rarely worked, I should add. All the breezes came from the south, so there was really no question of shutting the south windows. So in reality you smelled it when it bloomed whether you wanted to or not.

It is not a jasmine, despite its name, but a Cestrum. Cestrum nocturnum. It is related to the potato. It is hardy if given a south wall and a mound of ashes for the winter when it dies back. Or it can be brought to waist height from little plants set out every spring. Or it can dwell indefinitely in a large tub, brought inside in October, and set out in late May.

I remember one hot summer night in Paris when I was young, thinking what the devil was the matter with the night air which did not seem right for August. Ah. I figured it out. None of the above.