The eminent Edwardian gardener, Gertrude Jekyll, wrote in 1900 that it takes "half a lifetime" to decide what's best worth doing in a garden and another half to try to do it.

She was a quick study, of course. Most gardeners take a full lifetime to discover what's best worth doing and then run out of time. To sum up enormous wisdom for you in a sentence, the formula is simple -- that's the trouble, it's too simple:

Grow the most beautiful flowers you have ever seen or heard of, going through the year.

That is the formula for the best gardens. There are a few corollaries, just as in law school you study conflict of laws. Go by the above formula, however, and temper it as follows:

If some season does not greatly interest you, forget that season and concentrate your effort on the seasons you like best.

If hard experience shows you that for some reason you cannot grow good lilies, peonies, lilacs or irises, then concentrate on other flowers that do well for you, even if the ones you give up happen to be on your list of "most beautiful in its season."

Pay reasonable attention to plants for background that enhance all others. You may not be madly fond of yew, photinia, box, holly etc., but make room for them anyway, even if it means cutting down on your roses, azaleas and chrysanthemums that (let us say) you like much better.

Resign yourself to usable paths or walkways in the garden. Five feet is quite narrow, when you consider plants have a way of flopping over the edges and when you consider you will be trundling along behind a wheelbarrow or setting up sawhorses to trim fence posts, saw plywood and other pleasant chores.

Having wasted your substance, as you perhaps feel, on a wide walk and various evergreens, what remains of the garden?

First, consider a fish pool in full sun but as near the house as possible. For city gardeners a concrete pool 10 by 12 feet, outside measurements, is about as large as the home handyman can construct by himself. You are that handyman, and of course can press your wife, good friend or child into helping.

Over the years you will say it was the single best gardening decision you ever made, even though the sunny site you give it means that much less space for other flowers. The magic of dark clear water, goldfish and water lilies, to say nothing of dragonflies, justifies almost any sacrifice in other gardening directions. Or, if you can't manage what I suggest, you can buy a horse trough of galvanized steel. You can get a circular one seven feet in diameter, set it flat on the ground and cover the sides with what you like if the metal offends you. Boston ivy will cover the outside in one season, adhering right to the steel, or you can use fence wire and grow ivy, akebia, kadsura or anything else that strikes you as suitable.

We have now reduced the garden space further, and still we're not done. Make a place to sit that's big enough for a table and some chairs. Pave that place. There are whole books on paving, so read a few.

Now, with what is left you may want the center open and given to well-shorn grass. Some people adore grass. I do not. Some people like to cut it, usually with those machines that ought to be outlawed along with chain saws and other noisemakers. But say you must have a lawn, then have one and be done with it.

Otherwise, the center of the garden, usually the sunniest part, may be devoted to the best flowers, starting in late winter with crocuses, squills, wild anemones, aconites, snowdrops, millas, and moving right along to daffodils, commencing with the very early dwarf and intermediate-sized kinds, and with them various quite early tulips and Roman hyacinths, especially the blue (the white Romans are not hardy).

Then come such huge early (about April 10) tulips as the fosterianas, with the main-season daffodils in as wide an assortment as space allows. You will discover gradually which daffodils you like best, and you will concentrate on them.

Then come peonies -- you would want very early kinds such as 'Red Charm,' which are finished by the time other peonies start blooming. In Washington and similar climates you will give special attention to the kinds called "early" (though not so early as the super-early) such as 'M. Jules Elie' and 'Festiva Maxima,' to name two old varieties of utter reliability. You can also have some midseason sorts, but the late peonies are risky in our heat.

You may want a few tree peonies, which are not trees but woody creatures four feet high. They do not die to the ground in winter, but hold their woody branches, bursting into leaf and flower before the regular Chinese peonies.

Then you have tall bearded irises. They bloom for a month if you grow a number of varieties, and each clump lasts in bloom about two weeks. Not long. But long enough. When I grew some hundreds of varieties, I never regretted the end of iris season.

Among the most beautiful flowers of the season do not overlook Siberian irises. Try a few spuria irises also. They grow splendidly for some gardeners, not so well for others, so try them gingerly to see how they do. Later, Japanese irises are among the few garden flowers that may properly be called gorgeous. Try a few, and remember to keep lime away from them.

From April 15 onward for a month you have azaleas. You can have them both earlier and later, but I mention their great month, in which the Kurumes and Glenn Dales bloom. With them you can be as riotous, gaudy and vulgar as you please, or as delicate.

Then come roses, starting with such early shrubs as Rosa cantabrigiensis, with light yellow quarters massed all along its pendant stems. In some gardens the main season of hybrid tea and floribunda roses coincides with the peak of the iris season in mid-May, give or take a week or two. In others, the roses follow the irises, along with Oriental poppies. They have a short flowering season and their main color, fire-engine red, dominates everything else, and they make a gap when they die down soon after flowering. But a clump or two is hard to resist. It's up to you whether you grow some crown imperials and other fritillaries.

We're only halfway through spring and have not considered such shrubs as lilacs. Space is running out, and you probably will need more than half of all available space for the flowers of summer and fall, and perhaps some tomatoes. You can always encroach on the lawn and probably will, which is why I suggest doing away with it to begin with.

All those spring-blooming bulbs mentioned will be planted this month and next, as soon as possible, except for tulips, which go in in November.