Step-by-step primer on how to grow a thick lawn and keep it that way

Your house can only look as good as your lawn. Thus, every bit of care you give that carpet of grass will repay you with a thicker, greener, healthier-looking lawn.

Early in the season make a checklist of your lawn needs and then go to reputable lawn-and-garden people to get the materials you need for the job.

Fertilize lawns as soon as possible. Ones that have been fed earlier should be fertilized during April and May. Undernourished grass cannot give luxuriant growth.

If you had any crab grass last year, eliminate it this year. Early spring is the time to spread a crab grass preventer. This can be done by hand or with a small spreader pulled by hand or behind a garden tractor.

You have to get out early to beat the dandelions, but they can be defeated. As soon as the yellow blossoms appear, spread a weed controller. This can be spread right along with the fertilizer when you feed the lawn.

Test the turf for grubs. If sections of the lawn can be pulled up easily and seem to turn brown, you probably have grubs that feed on the grass roots. It is worth the effort to spread insect control in the areas where grubs are destroying the grass.

Some people are puzzled as to when to begin mowing the lawn. Most lawn experts tell us to start mowing before the grass blades grow tall enough to bend over. Bluegrass and fescue can be cut with a mower set at 1 1/2 inches. Bentgrass can be cut shorter, about an inch high. A good rule is to cut off no more than one-third of the grass at a single cutting.

Grass requires about an inch of water each week. If nature doesn't provide the water, you will need to water the lawn artificially. This can be done at your convenience, day or night.

A good lawn increases the value of your home, makes living there more enjoyable, and adds to the attractiveness of the entire neighborhood. Lawn-and-garden people maintain test plots and will share their knowledge without charge if you ask them. They are knowledgeable about materials for lawn care and can readily identify problems.

Scott's nursery is one that answers floods of questions phoned in by homeowners. Its specialists answer hundreds of calls a day during the growing season and welcome your inquiries. The nationwide toll-free number during weekday business hours is (800) 543- 8873. In Ohio, call (800) 762-4010.

Your county agricultural agent, usually located in the county courthouse, and your university extension service also have information available about keeping lawns healthy. Lawns are a major part of home- beautification projects and city-improvement plans.

Questions arise this time of year concerning the browned-out grass caused by a disease called snow-mold fungus. Use a flexible rake to break up the matted grass lightly, allowing the air to circulate. The sunlight needs to reach the crown of the grass plants to destroy the fungus. Follow this procedure with one of the new slow-release fertilizers, which will provide nutrients for the grass over a period of time. Much of the grass will recover by midspring or early summer.

In the future you can avoid snow-mold fungus by using a fertilizer in the fall, which contains a disease preventive.

Many lawns are reseeded or freshly seeded in the early spring. To prevent weeds from growing faster than the grass is always a problem. If you fertilize as you seed your lawn and include a crab grass preventer, you should have a minimum of weed problems in your new lawn. However, be sure to use a special weed preventer that will not harm the good lawn seed as it sprouts.

Preventives for broadleaf weeds are less successful than controls used after the weeds have grown. A good policy is to wait until the new grass seedlings have been mowed at least four times. Then apply a fertilizer that has been combined with a weed killer that controls actively growing dandelions and other broadleaf weeds.

This brings to mind another question. When should you mow your new lawn? A newly planted lawn can be mowed when it has grown two inches high. Cut it back to about 1 1/2 inches. If you have sown grass seed to thicken an existing thin lawn, mow whenever the grass needs to be mown. The old grass will cushion the new seedlings and the mower will not harm them.

Rules for raking the dead grass or "dethatching" the lawn have changed somewhat. It is not always wise to remove all the dead grass. After a hard winter, wait until the grass has begun to grow again and has been mowed to few times. The old dry grass offers some mulch and protection. The soil should be moist but not soggy when the lawn is raked.

If you find it difficult to remove the dead grass after the grass has begun to grow, or if it seems excessively matted, you can rent a thatching machine to remove the grass.

As you rake away the dead grass, beware of shallow-rooted patches of grass that grow in shady areas. The grass grows shallow- rooted because it competes with tree roots for nutrients. Avoid severe raking in these areas, as the grass will rake loose from the soil, leaving bare spots.

If possible, prune the trees to allow more sunlight to reach the grass. Additional watering and fertilizing may be necessary to maintain a good stand of lawn grasses there.

The length of time it takes for lawn seed to germinate depends on the type of seed, amount of moisture, and warmth of the soil. Lawn seed may be sown early in the spring as soon as the soil temperature has reached 55 degrees F. With one of the factors for seed germination missing, your lawn seed could fail to germinate.

The seedheads that form on some grasses, especially bluegrass, are part of the normal growing cycle. These seeds are little or no value to thicken your lawn. It takes a sharp, well-adjusted mower to cut the seedheads off. Your lawn will prosper more if you rake the seeds up so they don't smother other grasses.

Brown, circular spots from dogs often make unsightly scars on the spring lawn. It may help to flood the area with water. The spots can be prepared with sold or by seeding.

Perennial grasses, which do not die over winter, sometimes appear as clumps in the spring. These can be lifted out and reseedeD, since there is no chemical to destroy them without destroying the desirable grasses as well.

Rolling lawns used to be a more common practice. This tends to compress the soil, keeping moisture, air, and nutrients from the grass roots. Normal rains and mowing will usually allow clumps of grass that have been lifted by frost to settle back into the soil.

Early spring treatment of your lawn can make the difference between unsightly weeds and luxuriant, attractive grasses. Free information and question-answer services are maintained by many newspapers, seed houses, garden centers, and local agents.

You can get written answers to your questions by writing to Scott's Consumer Services, Marysville, Ohio 43040. A free two-year subscription to Lawn Care is also you rs by writing to Scott's Subscriptions, at the same address.