It isn’t easy to grow a great lawn, and it’s painful when the lawn ends up looking bad despite your best efforts. Here are potential causes of—and solutions for—the things that might be wrong with your lawn…

Bare and Thinning Areas

You might think that the simplest remedy to fill bare and thinning areas in your lawn is to loosen up the soil with a rake and then sprinkle grass seed. The problem with this simple solution is that there’s a good chance the new grass will fail as well. These sections of your lawn are struggling for a reason. Before you reseed, it’s worth trying to figure out why the problem exists. Ask yourself…

Is the bare patch in a heavily shaded area, such as under a tree? If so, one option is to reseed this area using a shade-tolerant grass, such as fine fescue. (Consult a local garden shop for guidance on which shade-tolerant grasses grow best in your part of the country.) But these grasses still generally need at least four hours of sunlight per day to thrive…and even if the grass you choose does thrive, it might look noticeably different from the grass of your surrounding lawn. An alternative is to stop trying to grow grass in the shady area and instead install a mulch bed and/or shade-tolerant plants or ground cover.

Examples: Shade-tolerant shrubs include gray dogwood, laurel and ­viburnum. Shade-tolerant ground covers include lily of the valley, sweet woodruff and periwinkle.

Is the bare patch in an area that is ­often walked on? If you reseed this area, use stakes and string to keep ­pedestrians off it for at least a month to give the young grass a chance to grow. But if you don’t want to face the same situation again in future years, rather than growing more grass, construct a path or patio using paving stones, concrete, gravel or other materials so that the grass doesn’t have to compete with people’s feet.

Is something lurking under your lawn? Probe down a few inches under the bare area. If there’s a large rock or the remains of a stump right under the surface, this might be creating a thin soil layer, inhibiting healthy grass growth. Remove the obstruction if possible…fill the hole with soil…cover it with a layer of topsoil, available in garden stores…then reseed.

Is there thick thatch where the lawn is failing? Thatch—the layer of old, dead blades of grass and other organic material immediately above the soil—should not be a problem as long as the thatch layer is no more than one-half-inch thick or so. But if the thatch is much thicker than that, it might be preventing enough rainwater from penetrating into the soil and preventing air from ­circulating around the bases of grass blades. Clear away thick thatch using a thatch rake and/or a gas-powered core aerator, then reseed. (Core aerators make holes in the soil beneath the lawn, which encourages growth of the microbes that help decompose the thatch layer.)

Helpful: Core aerators are available for rent at many home centers and rental centers, generally for $50 to $100 a day. Aerating helps with other lawn problems as well—see below.

Brown Patches

In the growing season, brown grass is not healthy grass. It might be possible to save the brown sections of lawn, but first you must figure out what is causing the problem…

Do you have a dog? The salts and ­nitrogen in dog urine can damage or kill grass in the spots where Fido often does his business. The most effective solution is to have the dog urinate elsewhere—ideally in a section of your property that is not covered by lawn or that is out of sight. If that isn’t possible, use garden fencing to stop the dog from urinating on the sections of lawn that are brown to give the damaged grass a chance to recover—or better yet, take the dog for a walk.

Meanwhile, water these brown patches heavily (and if the dog still is urinating on other sections of the lawn, water these sections heavily, too, as soon as possible after the dog has peed on them). If the brown grass does not recover, remove a two-inch-thick layer of the topsoil and add new soil before reseeding.

Helpful: Certain grasses, including St. Augustine and Bermuda grass, stand up relatively well to dog urine but are not appropriate for cooler climates.

Do you see insects or insect damage? Take a very close look at the blades in the brown area, as well as the still-green grass immediately adjacent to the brown area. Do you see insects and/or holes suggesting that insects have been eating this grass? Also, carefully peel back the sod—the layer of topsoil containing grass roots—near the edge of one of the brown areas to check for grubs. Grubs are small, soft, whitish larvae, often curled into small “c” shapes, that feed on the roots of your grass. Put a few samples of the damaged grass and/or the pests you find in a sandwich bag, and bring them to a garden shop or home center to ask if these insects might be causing the problem. If so, ask which insecticide is best. (There also are all-in-one insecticides that kill most common lawn-damaging bugs.)

Act quickly, before the infestation spreads any further. Be sure to purchase a “curative” insecticide meant to deal with an existing insect problem, not a “preventive” one designed mainly to avoid future problems. Follow the directions precisely.

Have you fertilized the lawn within the past few days? If so, you might have used too much in the brown ­areas, causing “fertilizer burn.” Water the brown sections heavily and repeatedly during the week immediately following fertilization to dilute the fertilizer, and wash as much of it as possible out of the topsoil and away from the roots of your grass. If this fails to save the damaged grass, continue watering to flush away as much fertilizer as possible from the topsoil down into lower layers of soil below your lawn where it will have much less effect on grass roots. Alternatively, you could replace the topsoil in these areas—then reseed.

Helpful: Fertilizer burn sometimes appears in long brown lines. This occurs when the person applying the fertilizer with a spreader makes passes that are too close together, resulting in double-fertilized strips.

Swampy Areas

Large, long-lasting puddles in a lawn do not just make it more difficult to enjoy the lawn—that standing water could lead to lawn-killing grass diseases or encourage mosquito growth as well. Potential causes and solutions…

Do you have a sprinkler system? If so, keep an eye on the swampy area as the sprinkler operates. Perhaps one of the sprinkler heads has stopped working properly and now is depositing an excessive amount of water in this spot.

Is the swampy area very near your house, driveway or road? The excess moisture might be the result of ­rainwater running off the roof or off a paved area into this part of the lawn. If so, divert water away from the lawn by improving or extending the home’s gutter system and/or adding French drains, buried drainage pipes or drainage ditches along the affected edge of the lawn.

Is there highly compacted soil and/or a thick thatch layer in the swampy area? If the soil is highly compacted, water might not be able to drain down through it properly. And a thatch layer thicker than one-half inch or so can act as a sponge, holding water in the area. Using a core aerator should dramatically improve drainage if either of these is the problem.

Is the swampy area in a low spot in the lawn? Use a shovel to carefully remove the sod, and set it aside. Add topsoil…walk over this soil to compact it somewhat…then add additional topsoil to raise this section of lawn to roughly the level of the rest of the yard…then replace the sod you set aside earlier. (Or if the grass in this area was dead, reseed.)

Additional options: If the do-it-­yourself solutions above fail to solve the swampiness problem, you could hire a landscaper to install a drainage system beneath the lawn—but that is a major project that could cost thousands of dollars. If you don’t want to spend that much, you could replace the lawn in the swampy area with a mulch bed that is raised perhaps one inch above the level of the lawn so that the swampy area is hidden underneath. Add plants that love wet soil, such as certain river irises…ferns…sedge…hydrangea…or dogwood. This is a beautiful-looking alternative.