With preliminary weed control efforts behind us, we begin another chapter in the orchestration of a spectacular fall lawn this year.

At the close of this third week of August, some important decisions have to be made, including what method you will use to dethatch the lawn and which grass you will be growing this fall.

Before deciding the future course, retreat once more to the lawn to make certain your renovation program is on target.

Disaster Lawn: Having applied Kleenup or Roundup to the lawn over the past week, it's only a matter of time before the weeds and brambles are dead to the roots. One week after that treatment, everything should be brown as straw. If you find any plants that have not died, spot-treat them this weekend with Kleenup or Roundup, either with a sprinkling can or the hose-end sprayer.

Treated now, those weeds will be dead to the roots by next weekend, time enough for final lawn work before seeding.

If the lawn is brown and dead, take out your rotary mower and scalp the lawn, using a grass-catcher and bagging the clips. This is your final mowing of the disaster lawn. The mower won't be used again until the last weekend of September, when you will be cutting the new lawn for the first time.

Since the mower will be in limbo for the next six weeks, consider removing the old rotary blade and having it professionally sharpened at the mower shop or hardware store.

If you did not apply Diazinon, Dursban, Dylox or Spectracide to the sunny lawn in the past two weeks, do so immediately after cutting the disaster lawn for the last time. Use the recommended spreader setting on the label. A good rain following the application will help, otherwise soak the lawn.

60-40 Lawn: Earlier this week, you should have targeted the second application of crab grass killer to the lawn with at least 40 percent good grass after having cut the lawn and bagged the clippings. This pretty much spells doom for crabgrass, goosegrass, yellow nutsedge and other grassy weeds.

Next, check the lawn to make sure that all non-grassy weeds are dead. On lawns without trees, your sprays of two weeks ago should have killed the weeds by now. Of concern for the moment are lawns with trees that received the Weed-B-Gon treatment only two weeks ago. On those lawns, make certain that all weeds have died. It is inevitable that some weeds will not have been controlled by the product, but an immediate application of Ortho Kleenup will take care of reluctant weeds.

The weed population dictates how to apply the Kleenup. If weeds are few, use an empty coffee can, adding an ounce of Kleenup and an ounce of water. Use a small paintbrush to paint the leaves of the weed.

If there is a large population of surviving weeds, revert to the hose-end sprayer. Add four ounces of Kleenup to the jar, do not add water, then spray the contents of the jar over a 125-square-foot area. This spot-treatment will kill weeds to the roots by next weekend.

Dethatching: While it is too soon to dethatch the lawn, it's a smart idea to plan ahead. The lawn surface will have to be cleaned of debris and organic litter before putting down seed.

If your lawn is less than 1,000 square feet in size, dethatching is best done by hand. You'll need one or more bamboo or flexible tine steel rakes, plus a dozen or so plastic trash can liners.

If you are renovating a large lawn, go with the powered machine, either the power rake or the verticut machine, available from rental stores. The verticut machine is the preferred machine for the job, but not all rental stores stock it. No matter which machine you plan to use, reserve the machine now. Ideally, you should dethatch sometime during the week of Aug. 27.

Dethatching the lawn is only part of the problem. The other is getting the debris up from the lawn surface and into plastic trash can liners for disposal. Even if you say you're in absolutely perfect health and you decide to hand-rake the lawn, you're going to regret the decision.

Take our word: Rent a Billy Goat vacuum from the rental store and automate the job. This machine, often with self-propelled wheels, will let you vacuum a 2,500-square-foot lawn in all of an hour, and you won't work up a sweat along the way. If you want to make things easy for yourself, reserve the Billy Goat machine now for the same day you plan to dethatch the lawn. The rental store may discount the price considering you're renting two machines at the same time.

Grasses: At the earliest, you should plan on seeding or over-seeding your lawn over the Labor Day weekend. Meanwhile, you have two weeks to decide the variety of turfgrass for the fall lawn. Choose your seed wisely so you enjoy one of the finest lawns of your life.

If your lawn is in full sun, many grasses will grow there -- bluegrass, fine fescue, perennial rye, tall fescue -- but do you really want to be a prisoner to the lawn that survives from one year to the next?

Our recommendations are:

The best turfgrass for sunny lawns is turf-type tall fescue; nothing approaches the excellence of these grasses, even Kentucky bluegrass. With tall fescue, you enjoy a superior lawn without worrying about summer drought. Just cut the lawn high (three inches) from Memorial Day to mid-September and, even if the heavens go dry, the tall fescue will survive. Under no circumstances should you use Kentucky 31 tall fescue.

The best choice for lawns that are up to 80 percent shady is fine fescue. It survives in full sun, too, but for lawns in sun and shade during the day, fine fescue is far and away the best choice. You won't regret choosing it.

As best as we can determine, here are the specific varieties you will find in garden shops, nurseries, hardware stores and home centers when you shop for grass seed (three-, five-, 25- and 50-pound bags in most cases):

Tall fescue: Amigo, Arid Arriba, Bonanza, Bonsai, Clemfine, Cochise, Crossfire, Guardian, Jaguar, Mustang, Rebel I, Rebel II, Titan Triplex (a mix of Bonanza, Rebel I and II), and Tribute. Do not use Kentucky 31, even if it is free.

Fine fescue: Common Creeping Red Fescue, Crystal, Highlight, Jamestown, Pennlawn, Reliant, Spartan, Victory and Waldina.

Kentucky bluegrass: America, Baron, Chateau, Cheri, Classic, Common, Georgetown, Glad, Gnome, Merit, Midnight, Monopoly, Nassau, Ram I and Touchdown.

Perennial ryegrass: Derby, Manhattan II, Palmer, Prelude, Repell and Tara.

Rough bluegrass (80 percent to 100 percent shade): Laser and Sabre.

Jack Eden is the host of "Over the Garden Fence" Sundays from 10 a.m. to 1 p.m. on WTOP Radio (1500 AM).