IN PERSIA, I read somewhere, there were 100 days in which the flowers were supposed to bloom, then the rest of the year you just looked for a place to be cool (or warm, depending on season).

And with us, you will notice there are those days in March that are pretty awful, in which all the advances of the spring are set at naught, and the life seems to drain out of everything.

For sheer gloom, nothing equals those prespring days (fortunately rare) in which you think the gradual buildup of heat and light since January meant nothing, nothing at all. Fortunately, in March the next day or two brings soft air, the color returns to things and life seems a 50-50 chance, after all.

Now this identical phenomenon happens again in July. A day comes when the light changes, and all the color and sparkle goes out of everything in the garden.

You can have sheaves of scarlet and lavender all around and it makes no difference. Everything looks secondhand, everythin looks old and tired, even if just coming into bloom.

Why is that? It is not just a subjective state brought on by eating too many Italian sausages and roasted peppers (a thing I weighed, then dismissed, as a cause) since other gardeners notice the same thing.

Fortunately such days do not go on; the sparkle returns and once again you are able to see all the weeds distinctly, in their full vigor.

I have completely eliminated certain weeds in parts of my small garden through the happy devise of adding a great deal of sand and rotted leaves for the irises.

I enjoy weeding that part. It has a completely new set of weeds, not found elsewhere. Purslane is the worst, or at least the most plentiful. It comes up easily, but then it revives easily. The great plantains do not like the sandy loam. They march in great thick squadrons around the perimeter where sand was not dug in. Sometimes I fear they are looking at the Promised Land and are ready to move in.

Plantains come out clean and stay out - they are not like those wretched pests (bindweed, ground elder and worst of all nut grass which fortunately does not like our cold winters) that rise like phoenixes from the very memory of having once grown there.

Plantains, besides, seem to me handsome. They were the badge of Richard the Lion-Hearted. They do not look as much like weeds as zinnias do, though of course plantains lack the showy flowers.

They cannot be allowed to remain, though. Nothing is better at smothering treasures in the garden than a good crop of plantains. Often gardeners, I notice, secretly admire their plantains (and dandelions are in this same league) just long enough for them to set seed, then they vigorously pull them out, knowing deep down that of course there will be millions more next year to admire. And pull out.

Water lilies are a comfort on the hottest days. Needless to say, you have to have a pond or pool or tank for them. Sometimes I invent reasons for climbing into the pool - say a trowel has disappeared; very likely it was pushed into the pool by the hound? Of course it is never in the pool at all, but the search can occupy 15 well-justified minutes of slopping about.

The water lilies at the National Arboretum do not have the look of luxuriance and contentment I expect.

It is always a jolt to see plants not very well grown at great places. At the arboretum, my diagnosis of trouble is all those fountain jets squirting water for no earthly purpose (water lilies and I are in full agreement on the general folly of waterworks) and then, possibly, not enough attention is paid to giving them good stiff soil - they do not really require fertilizer, no matter what you read - and replenishing it every year. Anyhow, my own water lilies are much handsomer than theirs, possibly because I value them more.

The daylily collection at the arboretum is a great pleasure to see. There was a period, a few years ago, when perhaps labor shortages or - I don't know why I say that. The trouble was nobody gave a damn. Or not enough.

But now the collection has many newer varieties, some of them blooming with quite astonishing freedom.

When you see something radically improved, it is never an accident. Those working with the collection now are clearly dedicated gardeners, devoted admirers of the daylily, and this all shows in the blooming season.

The Lord knows I have trouble enough myself. It is partly a question of memory, which fails as middle age approaches. This past week it finally got to me that the thing I have been meaning to look at was my infant cut-leaf golden elder. It escaped notice when some violets (benefiting from some cottonseed meal administered to a nearby plant) took to growing like rhubarb and quite overung the young elder. Indeed, I weeded out the violets just in time.

Tastes vary. For me, nothing is worse than plants far apart. Left alone, nature plants densely and so do. I. Of course one pays for this in great suffering.

The scarlet lychnics with the purple leaves, that I so valued, was overwhelmed this year by the baptisia.

Everyone knows the baptisia, a valuable plant for foliage and blue flowers and generally graceful habit, "does not require staking." No.It does not flop about like baby's breath. But it does require space in which to luxuriate. Although its stems are off the ground, it billows forth like a lion after a bath.

It has completely shaded out the lychnis. Last year, when the lychnis was so handsome, I was complaining the baptisia was not growing as well as it should. Possibly there is a moral here. But then most of us already know we expect our gardens to do quite impossible things, and are no end put out if they fall short.