The common denominator in this weekend's garden is survival. In the midst of one of Washington's driest summers in nearly 20 years, on top of an absolutely dry-as-a-desert spring, hope is waning for a turnabout in the weather pattern that has shunted rain clouds far to the north. As July gives way to August, there is really no question about the future of the landscape. Its survival rests entirely in your hands.

Which of the crossroads will you take? Will you dismiss the spiraling water bills in an effort to save shrubs and trees, or will you choose to become a spectator while the garden passes into oblivion?

If you choose the latter, know that this is the first chapter in a serial that will cost a fortune before it's over. Remember, dead shrubs and trees will have to be dug from the soil and carted away. Then, replacements will have to be bought and planted.

Knowing these eventualities, the only choice is to water the landscape while the water supply lasts. Water trees and shrubs first, remembering that spring flowering plants need copious amounts of water because they will start producing the buds for next spring's flowers in the next two weeks; the cycle continues through mid-September, when all buds and spurs will be in place. Last in water priorities would be vegetables, lawns and flowers.

Here are some water-conservation ideas to consider: Water the soil around plants without allowing water runoff. Soaker hoses adjusted for a reduced water flow are perfect for soaking shrubs and trees. Encircle the dripline with the hose, then allow a lazy flow of water to saturate the soil without running off.

If mulch covers the soil, build a temporary dike from poor soil so it encircles the tree some six inches beyond the dripline, then recover with mulch to hide the dike. There will be no runoff from here on. Soak thoroughly for an hour or two, depending on plant size. Elsewhere, use available sprinkling equipment, but time your watering to minimize disease problems. Oscillating and impulse sprinklers are perfect for vegetable gardens, with morning watering in your best interests. Dust leaves with kitchen flour afterward to maintain some semblance of insect control without relying on chemicals. While lawns are vulnerable, summer brown-out isn't symptomatic of dead turfgrass; thankfully, the reverse is true. Given frequent rains, the lawn will recover and return to its predrought green color.

Meanwhile, try to water segments of the lawn in the early morning hours, deep-soaking the areas for an hour or two. By relocating the sprinklers every night in preparation for the morning soaking, you minimize the work involved; activate faucets early to take advantage of the precious hours before the sun is overhead.

Cut as high as the mower will go, but don't cut unless absolutely necessary. Tall grass shades the soil, further conserving moisture in the top inch of soil. The price of saving shrubs and trees could well be the decimation of the flower bed. Once-a-week soaking will save the plants, but don't go overboard, especially if the bed is mulched. If and when the rains return, the flower bed will recover faster than other parts of the landscape.

Apart from the watering crisis, a host of other jobs need tackling in the next week: Azalea cuttings of early July will be ready for transplanting next week.

Use 4-inch plastic pots filled with your standard 1-1-1 mixture (that is, equal amounts of milled or compressed sphagnum peat moss, perlite and vermiculite). Wet the soil before filling your pots almost to the rim. Scoop out soil to accept the rooted azalea cutting, then move the cutting into the pot with a teaspoon.

When all cuttings are in their pots, move them to a fully shaded area outdoors (or a shaded, screened porch), keeping the soil lightly moist by every-other-day watering. One light application of fish emulsion will benefit the potted plants, but do this immediately after transplanting.

Pots should be sunk in the ground after Halloween so plants spend the winter outdoors. In mid to late March, pots are unearthed and plants are set into permanent quarters in the garden (morning sun, afternoon shade). Dead branches on azaleas are not an omen of drought, but rather an expression of azalea petal blight. Cut the dead branches now, but mark the shrub with a ribbon so you will remember to spray for disease control next April. Tie ribbons on just-fruited canes of raspberry plants so you will know those to cut and those to save.

Consider bending these ribbon-marked canes over to the ground and burying the tips in soil; keep the soil lightly moist and new raspberry plants will grow at the tips over the fall and winter. Come late March, you'll cut the tips (then rooted plants) for The concept is to fertilize and water to promote growth of all weeds in the next two weeks.planting in the garden; then prune the surviving canes back to the ground.

Those tall canes now on the plant (without ribbons) will give you raspberries next July.

Much of next week's column will be given over to the International Lawn, Garden and Power Equipment Expo that opens Monday in Louisville, so let us get a jump on the lawn program right here and now.

As of now, lawns fall into one of three categories: a near-perfect lawn without problems . . . a lawn of grass and weeds, with the grass making up at least 60 percent of the lawn and weeds less than 40 percent (the 60-40 lawn) . . . and the lawn that is an ocean of weeds and little if any grass (the disaster lawn). The latter two lawns will be undergoing renovation in August, so let us set the stage for the events to follow. The 60-40 lawn. Continue your watering program. Over the Aug. 1 through 3 weekend, you will apply chemicals to destroy weeds; seeding of the lawn is scheduled for the Labor Day weekend or the first week of September.

Meanwhile, do not cut the lawn to allow optimum weed growth by next weekend. Shop for your products in the next few days.

For lawns with trees, you will need Ortho Weed-B-Gon (liquid concentrate only). For lawns without trees, you will need 33 Plus (liquid) or Security Chemicals' Super D-II Weedone (liquid). On sunny lawns with crabgrass, goosegrass and yellow nutsedge, you will need the gallon container of Rockland Chemicals' Super Crabgrass Killer. Details are forthcoming in next week's column. Disaster lawn. Over this weekend, adjust your rotary mower for the lowest possible cutting height and scalp the lawn; if you have a bagging attachment, use it to collect the debris. Afterward, mix up some water-soluble plant food in the hose-end sprayer and fertilize the disaster lawn.

Consider MiracleGro or RapidGro, adding two or three tablespoons of the granules in four ounces of water . . . stir to homogenize the granules in the solution . . . then add to the jar of the hose-end sprayer and spray uniformly over the lawn; if your lawn is immense, add more fertilizer.

The concept is to fertilize and water to promote growth of all weeds in the next two weeks. Meanwhile, shop for the products to put the weeds away.

For lawns of 1,000 square feet or less, buy a quart container of Security's BlotOut or Ortho's liquid concentrate Kleenup; both are discounted to about $11. For lawns larger than 1,000 square feet, pick up the quart container of 4l percent liquid concentrate Roundup (discounted to about $35); when you shop, see if there is a 63-page tiny booklet inside the plastic sleeve on the rear of the plastic container. Given a choice of quart containers, you would rather buy the one with the book than the one with a tag of instructions.

Do not buy the quart container of Roundup L&G that is the l8 percent concentration because it costs substantially more per treatment than the 41 percent Roundup recommended.

Specifics of the lawn treatment will come in the Aug. 9 column.Jack Eden hosts "Over the Garden Fence" Sundays from 10 a.m. to 1 p.m. on WTOP Radio (1500AM).