AN ALL too common experience faces the new gardener who acquires a small city or suburban garden -- he has the land, maybe 20 feet wide, maybe 40, and little idea just how to begin transforming it into a major pleasure of his life.

The garden will need to be enclosed. A fence, wall or screen of plants will do it, provided they are six feet high.

Dealing with reality, rather than fantasy -- there is not much point dreaming of a fine eight-foot brick wall at today's prices -- the best solution will probably be a wooden fence, either palisade of touching boards or poles bound together or a board-on-board fence of redwood or western cedar.

If that cannot be afforded -- it may cost $2,000 for a town garden, but it depends on the size, and the gardener should get prices before giving up -- wire fencing will have to do.

Chain link is ugly, and is made worse by its association in the mind with industrial plants and parking lots. It does have the advantage of strength and stability.

It should be concealed as quickly as possible. If it is painted black and shrubs are planted along it, it need not be an eyesore at all.

If it is only 42 or 48 inches high, the gardener may use American, Chinese or English hollies, photinia, nandina, evergreen euonymus, rhododendrons, osmanthus, upright junipers and yews, azaleas (tall growing sorts and preferably large specimens to start with, for prompt screening results), certain cherry laurels and leucothoes, and, in short, most hardy broadleaf evergreens and neat compact conifers that do not turn suddenly into forest trees.

If the fence is six feet high and the garden small, it may save valuable space and provide a better sense of scale to cover the wore with vines. Ordinary English ivy is effective, and it will take three years for it to get going.

The almost-evergreen Akebia quinata is delicate in effect and robust in growth. It is effective and astonishingly handsome if grown on such a fence and clipped occasionally, to thwart its desire to send off shoots in search of nearby shrubs and trees.

Vines that drop their leaves in winter still have their bare stems and still do a good job of concealing the wire. Grapes are as beautiful as anything; cheap and utterly effective all the leafy season, but they do not leaf out until the spring is getting warm and are disappointing as a background to the early flowering bulbs, from snowdrops to tulips. They are in leaf by the time tall bearded irises bloom, however.

A deciduous climber valuable for late summer (August-September) bloom is Polygonum auberti, which grows very rapidly even the first year and has admirable showy feathery white panicles. It grows to 40 feet.

The Japanese clematis, which we may as well call C. paniculata, is excellent.

This nearly evergreen vine (the correct name is now C. maximowisciana, and I am not sure I will go along) has small starry flowers, scented of hawthorn or almond for the several weeks around Labor Day.

Like the other plants mentioned thus far, any fool can grow it. And yet the most sophisticated gardener will not find, among any rarities, a more superbgarden plant.

The common Chinese wisteria will cover the wire fence quickly, and afford its beautiful blooms in April. It will require (like the polygonum) occasional whacking to keep it in bounds, and of course it drops its leaves in Novermber.

A combination of vine-covered wire fence and occasional stretches of evergreen shrubs is, of course, possible. Also, if the garden does not require a total screen (a gas station next door, for example, suggests a total screen) some deciduous shrubs, or even small trees, may be used in the general screening. Obvious fine applicants for the honor are the various viburnums, star magnolia, Venetian sumac, lilac, mock orange.

Just here the gardener has to consider whether to allow things like lilacs and mock oranges which have dull undistinguished foliage, however delightful their blooms. Certainly, they should be used sparingly, since they contribute nothing to the general effect except the few days they are in bloom each year. In a small town garden, one specimen would surely be enough.

You will also consider that a screen of broadleaf evergreens will look better if they are not all 8-feet high and solid. That is, some hollies with an occasional clump of lower-growing nandina or some tall photinias with some lower-growing mahonias in front will give a happier effect than a solid row of tall plants.

Also, the inclusion of occasional shrubs like barberries, blueberries, Chinese witch hazels, trifoliate orange, rugosa or other relatively trouble-free shrub roses, will prevent the somber and somewhat heavy effect of too many evergreens.

It is a question of balancing the need for screening with the need for avoiding too massive and forbidding an effect.

Of course, a hedge of hollies or yews, 6 or 8 feet tall, is incomparably comforting and rich-looking, but somebody will have to clip them and this is more trouble than one usually thinks it is going to be. Also, a hedge keeps growing in girth. Every few years, unless it is to expand in width indefinitely, it will have to be sawed back and will take a couple of years to regain the solid look desired.

A hedge, in other words, is by no means trouble free or always handsome.

Often the garden, even with a 6-foot fence, gives a fine view of some architectural horror, like a cinderblock warehouse. In this case, use a sweet bay magnolia, a dogwood, a crabapple, a Virginia fringe, etc., to screen it. If the eyesore is three stories tall, obviously a small garden cannot afford a three-story plant to hide it. But a 10-foot plant will do the trick if it is planted nearer the viewer than the eyesore.

If you stand at the Capitol and look toward the Monument, a barrier the size of your hand held 2 inches in front of your eyes will completely block the Monument. But a 300-foot sequoia tree will not block the Monument if it is close to the Monument. It is obvious, and therefore often forgotten, that the nearer the eye, the lower the barrier needs to be to block the distant view.

Another thing commonly forgotten is that the warehouse or other eyesore often need not be entirely blocked from view. A plant can obscure it partly, and often that is enough.

Another thing worth noticing is that a striking feature in the foreground will render a distant view almost invisible, psychologically. If the garden is surrounded by high-rise buildings, for example, obviously they cannot be screened from view by planting a hedge of 60-foot evergreen magnolias (though one friend of mine is determined to do this, despite my protests).

The thing to do is to make as attractive a background to the garden boundaries as possible -- a rich textured look through the use of hollies, yews, nandinas and so on, as already recommended -- and then to focus the eye on a feature well inside the garden, like a circular summer house (probably a tool shed in real life) or a pool with brick coping or an oversized urn or pot or strawberry jar with sedums and houseleeks. Or and arbor over a table and chairs of specially handsome design, or a mass of flowers in the foreground nearest the house. When the distant view is unattractive, that is not the time to arrange a clever vista leading he eye straight to it.

Once the background is achieved, the gardener can tend to such important matters as paved paths. A small garden may have one path -- of brick, stone, slate, concret -- concrete is as handsome as anything if cast in separate blocks, used as flagstones, and the finishes are endless, as any concrete manufacturer can demonstrate.

Never try a path of grass, thyme, chamomile, or any other plant in a small garden. It will not stand the traffic, though a similar path in a garden of some size might do well.

If you want gravel, have it. I cannot admire it, myself. It is never firm and steady; it is unpleasant to walk on; it never stays in place and is always being tracked into the house and all over the rest of the garden, and it does not look very well in the first place.So much for gravel.

I might add that gravel promptly fills with weeds and oddments of dead leaves. You may have trouble with grass elsewhere but it flourishes mightily in a gravel path. So if you like gravel, for some odd reason, I suggest using it over a slab, and I suggest allotting numerous Saturdays to keeping it neat.

Of all the Old World notions, gravel is the dumbest; so I am not much surprised to see the walks of the Mall in Washington newly laid in gravel. Anything else would have made too much sense.

Walks should not be narrower than 4 feet, unless it is strictly necessary to cheat on the width -- as it often is in tiny gardens, or as it sometimes is to preserve a reasonable scale. But unless there are special reasons, a walk 4 to 6 feet works best.

At this point -- the instant the enclosing framework of the garden is started on -- a sitting place should be begun. A slab of dressed wood makes a good bench (2-by-12-by-72 inches, say) with maybe a small slatted roof with a vine over it for shade, the whole supported by two 4-by-4 posts, and bench set against the house wall.

The garden may be too small for anything much larger. If so, the bench is given dignity and importance by being set on a small brick or stone pavement.

In relatively vast gardens of 30 by 35 feet there should be a table and some chairs, small in scale but not designed for dwarfs.

Also, at just this point, I would decide on the pool. It should be between 16 and 24 inches in depth. It may be as imple as a large washtub faced with brick.

I am convinced, after some years of observation, that a fish pool should be as large as possible, and is a worthier object of sacrifice (if money should, for some reason, run short) than almost anything except the enclosing framework of the garden.

Cornmeal is highly nutritious, and if the family is fed on it for a few weeks, much money can be accumulated for the fish pool.

Good sizes for small gardens are 6 by 8 feet, 10 by 12 feet, or a circular pool 6 to 10 feet. I would take the pool very seriously, not as a mere passing optional fancy.

It should be located in full sun, if that is convenient, otherwise in full shade, if that is necessary. The mirror magic works equally in sun or shade. But only in sun (or part sun) are water lilies possible, and the fish are happier and the blue sky and garden flowers reflect most cheerfully.

Forget fountains, underwater lighting, unless you really cannot live without them, and then be quite sure in your mind you know what you are doing. I have known nice pools ruined by such gimmickry and that goes for filters, too.

I suppose I should say the lily pool is not intended to be a swimming pool. And needless to say, make sure tots do not fall in it.

A final warning, to save you trouble in the long run:

Do not try to scrimp on materials. If you need wood, get good wood. Wood that rots in three years is no economy. Paving at half the price is not a saving if it looks a tenth as good. A pool that keeps you in constant anxiety for leaks is costlier in wear and tear over the years than one made correctly of poured concrete or ready-made fiberglass or steel.

Do not scrimp on scale.Do not attempt a reproduction of the Matterhorn in miniature. You cannot have everything, even in huge gardens. A reasonable width for flower beds is 4 or 5 feet, and no point is served by seeing how tiny they can be made. If there isn't room for them, forget them and use a willow tree in a tub. Do not try to jam a table and four chairs in space 5 by 7 feet merely because you have measured and found it can be done. Leave room to breathe and walk in and out.

Try not to be greedy. I am a fine one to say it. Do not try a rock garden, an arbor, a pool, a lawn, a terrace, a little copse, a bit of meadowland with poppies, all in one tiny garden.

On the other hand, do not be afraid to turn the alley gate into a feature, with perhaps a small arbor built over it for honeysuckle, with a water tank for fish beside it. Garden features cannot be endless, but where there has to be a necessity like an alley gate, try to make the most of it.

Next week, God willing, we shall ponder what flowers and other ornaments to put in the little space left to us, once the garden enclosure and screening has been done and the path or paving and bench or sitting place has been (grudgingly, perhaps) allowed for.