SOMETIMES GARDENERS miss the opulence of summer and wonder what, exactly, is wrong.

Now there are gardeners who want the garden to look as good as possible in January, say, and therefore plant a lot of hemlocks, yews, ivy and so forth on the theory they are bound to look fine in the winter -- and bound to give the garden a furnished look at all times.

Sometimes the effect, however, is like the bottom of a well: dank, oppressive, glum. And while it looks green in winter, all right, it can look heavy at all seasons.

There are a lot of gardens like that in Georgetown and other congested, jammed-up neighborhoods. Two quite simple additions can do wonders for dismal funerary gardens:

First, a pool in the sunniest spot. It should be larger than seems reasonable. Most things in gardens look better if over-scaled; that is, they look best if made too big.

The second thing is to introduce vines -- a grape. For some decades now I have kept my eyes open for climbing plants. I yield to nobody in my fondness for kadsuras, akebias, clematis, campsis, honeysuckles, Virginia creepers, moonflowers, morning glories, creeping figs, climbing roses and so on. But no other vine catches the light in just the way the grape does, and no other vine I can think of makes a pattern, a color, a texture, a canopied shade, quite like the grape.

Often gardeners with glum courtyards think maybe some tubs of nicotiana or bright yellow marigolds will help. Far less trouble, far more effective, is a single grape vine. What sun there is will be caught by the grape leaves. The grape is a plant that at once lightens the effect of too many yews and adds luxurient solidarity to frail designs.

Such a vine is entirely too heavy to be allowed to grow over other plants; it will smother everything. In very small gardens, however, a grape does very well on a 4-inch wooden post. In larger gardens, it can wend its way along chains or ropes, or grow over an arbor above a bench, or over a summer house.

A grape vine in sun, with yews or dark evergreens in the background -- the evergreens lightened perhaps by a plant of the wild Japanese clematis -- will provide as much contrast as you really want.

In small gardens, the effect seems to me better if you see that large pool (even if space limits it to 6 by 8 feet) through some slight barrier -- say, a pole with vines at one side, between the place where you sit and the water itself. Needless to say, the "barrier" should be mainly an illusion and not blocking the view of the water.

Beyond the water, and reflecting in it, there ought to be a few (or many) flowers that really show up, such as lemon-yellow or white things. Marigolds need not be despised, nor daylilies or roses or lantanas or dahlias, zinnias, nasturtiums, etc. Lemon or canary yellow shows up the best.

I am always at the odd things gardeners are tempted to, in the handling of their lily pools or basins of water. Even books on design, which should be better than most of them are, seem determined to surround the pool with some sort uf fuzz.

The pool, on the contrary, usually looks best if there are no plants whatever around it. A bathtub in the middle of the living room is exactly what you want, and I overstate it a bit.

The pool should be brim full. There should be no statuary in or near it. Fountains should be avoided, unless the water arcs into the pool from the wall. The pool in a small garden is going to be too small, to begin with, so heroic restraint is called for not to clutter up its margins or surface with gewgaws.

It may be hard to believe, but water itself is more ornamental than the junk sculpture commonly introduced, and in a small pool Maillol, Henry Moore, Phidias, della Quercia, and vinyl gnomes are equally junk. Small pools, in fact, are usually decimated in their effect by the introduction of plants or works of art, admirable in themselves, but cluttery in their effect by the pool.

Every pool that has a statue or a fountain should have it temporarily removed. Almost invariably, you will like the effect better. If not, pull it back, and God have mercy on your soul.

Sculpture can look fine, set some distance back from a pool. Assuming, of course, it looks fine to begin with, which it usually does not. The garden at Sissinghurst, the Nicholson-Sackville-West garden in Kent that everyone rightly admires, is damaged by the owners' unfortunate fondness for quite ugly sculpture. There isn't much of it, but what there is manages to damage a considerable area around it. If you have a piece of sculpture you want in your garden, you might try setting a small water basin in front of it, against a wall, rather than sticking it on a pedestal in the pool where its chief function will (as like as not) be to impede swimming fishes.

Very well, class. We have it now? Yews and darkness in the background, a pool as large as seems sane in the brightest sun, a grape vine to catch the sun, a brimming fullness of water, no fountain (put the fountain against the wall and let it gurgle into a basin, not the pool) and no sculpture or rim of ivy or anything else around the pool, at least not on the side you view it from. And in the distance some vines up on poles or columns or whatever, to give height, and shining through them some bright yellow flowers. If you have sculpture somebody gave you, or that you bought in a fit of error, try putting it in the dining room with a spotlight on it, or let it preside over the rabbit hutch or dog kennel.