No matter what kind of new grass you planted, and no matter how it was started, whether from sod, sprigs, plugs or seed, it requires special care. All new grass is tender and vulnerable to trampling and drying out. Until your new lawn has established, treat grass like the baby plant it really is. You'll need to water, feed and handle it with gentle, considerate care. If you do this, you will--in most cases--be rewarded with a lush green lawn in just a few months to a year.
Keep people and pets (if possible) off of new grass, especially during the first month. This may mean you have to put up a sign or even a physical barrier (temporary fencing) around the edge of the new lawn. New grass needs time to develop a good strong root system--trampling from feet or heavy paws disturbs young undeveloped roots.
Water new grass often. Adequate water is especially important for new lawns. New grass simply will not survive drought as the roots are still shallow and poorly formed. Keep soil moist for the first two weeks. According to New Mexico Gardeners, nmmastergardeners.com, the first two weeks are the most crucial for seeded lawns. Start with shallow but frequent watering for seeded lawns, keeping the soil moist at all times. For new sod, follow the suggestions of New Mexico Master Gardeners and water to a depth of 2 to 3 inches each time.
Wait to mow. Yardener.com recommends waiting until sod-started lawns are at least 3 to 4 inches high before mowing. The reason for this is the same reason you should keep pets and people off new grass--mowing can disturb the young roots.
Fertilize new grass only after six weeks, as suggested by Greenvelvetlawns.com. When you do apply fertilizer, the website suggests applying at a rate of 1/2 lb. of nitrogen per 1,000 square feet. But you may need to adjust the amount and rate for your grass type as fertilizer requirements can vary.