In the spring many home owners get an urge to patch up the lawn. It is not the best time to sow grass seeds but it can be done successfully. The problem is to get the grass growing well before crabgrass starts to appear, and to have the grass somewhat established before it has to cope with hot, dry summer weather.

The first decision is whether to do the whole lawn over or just make repairs. If you have grass fairly well distributed over 50 per cent of the lawn, it is better to repair than to start over.

Try to figure out why there are bare spots and see if it can be corrected. Seeding or sodding alone will not be a permanent cure. The new plants will die for the same reason the old ones did.

A female dog can cause bare spots. In such cases, the old soil in the damaged areas should be removed to a depth of 3 or 4 inches and replaced with good soil.

Too heavy a salt concentration from winter use of salt for deicing, can kill grass. Usually leaching will take care of this in a year or two.

Hard packed soil could be the problem. Heavy foot traffic when the soil is wet, or use of a heavy roller or other equipment, can cause soil compaction.

If there is constant heavy foot traffic in a particular area, perhaps a hard-surfaced walk is the best answer.

An easy way to fill bare spots is by sodding. Chunks of sod can be taken from inconspicuous places and used to fill the bare spots. Or, buy a few rolls of sod and cut it into pieces of the required size.

To seed the bare spots, use grass seed of the same kind that is prevalent in the lawn. If you don't know what you already have, make a guess.

Don't just throw seed on and expect Mother Nature to do the rest. It isn't as simple as that. First get rid of the weeds. Then use an iron rake to scratch up the soil. Sow the seed and press them down into the soil with your feet or a roller.

Moisture is a critical factor in grass seed germination and survival. A mature seed contains a small living plant that is dormant. This miniature plant is the embryo. When conditions (temperature and moisture) are favorable, the embyro starts to grow. This process, including bursting of the seed coat, is germination.

If the embyro dries out at any time after it starts to grow, it dies. That is why it is important to keep the seed bed moist. After the plant is up and growing, water instead of sprinkling, if rainfall is inadequate. The grass needs about an inch of water a week. New grass, with a limited root system, cannot survive drought as well as established grass.

Lawn grasses with a good roots system have the ability to crowd out weeds and keep them from becoming established. Mowing has a profound effect on the root growth of grass.

One of the worst mistakes is to let the grass get too tall and then cut off too much of the green matter at one time.

The green blades of the grass produce the food of the plant. The raw materials come from the soil and air.

If most of the green part is removed, root growth stops for several days or even two or three weeks, and the plant experiences shock.

No more than one-third of the green part of the grass blade should be removed at one cutting. If the grass is 3 inches tall, remove 1 inch, cutting it back to 2 inches.

If the grass is 5 or 6 inches tall, remove only 2 inches the first mowing, and four or five days later remove another inch.

The grass should not be cut when wet unless it is absolutely necessary. Dry grass cuts more easily, does not ball up and clog the mower, and the lawn looks better after mowing.