TIME TO think of spring planting, you know, unless you have a morbid interest in winter, and wish to dwell on the misery of mankind.

Rhubarb -- and let me say people really do inquire about the most astonishing things -- is best planted in late winter or as early in the spring as roots can be got.

If you order it from a mail-order house, you should request delivery March 1, and I imagine you will receive your roots by mid-April. It's not so disastrous as you might think, since you can't cut the rhubarb stalks the first year anyway.

About half a dozen varieties seem to be offered nowadays -- 'Valentine,' 'MacDonald,' 'Victoria' and so on -- and probably there is some difference in flavor.

Some are certainly redder in the stalk than others, though when cooked they are perhaps all a rather hideous puce-mulberry tint.

Since I have only eaten rhubarb once in my life, I am unable to advise which sorts are best to stew up with sugar.

But I do admire rhubarb for its foliage, which is handsomer than most things grown for handsome foliage. My great favorite of the whole batch is the inedible for at least I never heard of anybody eating it) giant sort called Rheum palmatum, 'Bowles' Cirmsco.'

This and other forms of this giant type have leaves two or three feet wide, reaching shoulder height by mid-May. At enormous effort, I once acquired a plant of it from England (not knowing an American source for Rheum palmatum, though there must be gardeners who grow it), but it died with the first blast of July heat.

The leaves even of the edible rhubarb are said to be poisonous -- oxalic acid, as I recall -- so when you cut the stems to stew them, do not have a fit of economy and decide the leaves would make nice greens. No, they might prove terminal greens.

Even the ordinary edible rhubarbs look handsome not only in the vegetable garden but also in the flower border, or among roses. There is no point, however, in hoping the handsome rhubarb leaves will somewhat disguise the bare portions of the rose bushes when they get blackspot, since rhubarb leaves begin to look terrible in June.

Another creature that should be planted in March is the grape. I can ususally tell when any plant ought to be set out, since a flurry of inquiries usually pours in about six weeks after the correct planting time, and everyone asks about grapes in May.

I yeild to nobody in admiration of the grape as an ornamental vine. Producing fine fruit is something else, and requires a good bit of spraying, not for two different mildews, but also (and especially) against brown rot.

Any garden center that sells chemicals with which to spray grapes can also give you a schedule for spraying them, but roughly you spray from early May until early September, every two weeks.

Without any spraying at all, a good bit of fruit can usually be harvested, but do not vaunt yourself if you get excellent crops at first. (If you plant the vines this March, you should get your first fruit late in the summer of 1984, and may have excellent harvests for two or three years after that). The organism that causes rot takes a while to build up in the soil.

At first I got spendid crops on 'Steuben' but last summer not a single cluster, thanks to the rot.

Beginning gardeners may wonder why the blue 'Concord' and the white 'Niagara' are grown so widely, since there are dozens of other varieties of much higher quality.

Neither 'Concord' nor 'Niagara' is disease-free, but both of them manage to produce fairly heavy crops, no matter what.

The best home-garden grape I personally know of is 'Villard Blanc,' but having said this I shall probably never get a decent grape from it again. It is of desert quality, though usually grown for wine.

For some reason the mockingbirds do not care for it. Since it is not widely sold, I should say I bought mine from Bountiful Ridge Nurseries, Princess Anne, Md. You eat it skin and all.

Two other American grapes (though 'Villard Blanc' is French, but half its genes are from American grapes) with excellent reputations for good health are 'Alden' a large blue grape said to be of excellent quality and 'Monticello' a black grape of much better quality than 'Concord,' not that that's saying a great deal.

My plants of these two varieties are now old enough to bear this summer, though I am old enough not to believe that any high-quality grape can be grown without care or spraying.

'Buffalo' is a grape that comes in mid-August with blue clusters that hold on till October. It is intensely sweet and vinous, though of 'Concord' type. It fruits heavily and does especially well grown over a summer house or arbor.

It must be full of vitamins, as mockingbirds arrive from as far as Connecticut, I believe, to feast on it.

You may conclude it works best to buy grapes at the grocery. Certainly you are not going to grow anything as good as 'Ribier,' or the other Californians.

I never spray the vine, and despite a certain amount of rot and a very large amount of mockingbird raiding, I have more than I wish to eat.

You can encourage your wife to make jelly, which in many cases will sit on the shelf for several years until thrown out, and jelly-making is educational for the kids to observe.

Some gardeners have wives who flat refuse to make jelly, grape juice or anything else from grapes. I have heard of a Rainbow Tart in which walnuts are mixed into a crust of dough, which is spread with cream cheese and concentrated frozen orange juice. Then grapes of different colors are put over the orange cheese, and a glaze of red currant jelly over everything.

If anybody has ever eaten such a dish, or ever does. I'd like to know how it turned out.

No ornamental plant is more precious to me than my grape vines. Their beauty seems to me unparalleled. I can imagine a garden of nothing but grapes and figs; it would be beautiful. What other plants give so strong an impression of opulence and well-being?

But I will have no part in the propaganda that leads the innocent to think grapes of the highest quality will be there if you just plant a few vines.

No. But they will be beautiful, and if you eat pretty much anything, you'll probably enjoy eating the grapes, and in any case, I do indeed guarantee the catbirds, the mockingbirds, the wasps and all their friends will bless you.