Spring Lawn Seeding
Spring is the time when many homeowners want to repair the damage done to their lawns from a rough winter or neglect from previous seasons. Turf professionals generally agree that late summer or early fall is the best time to sow grass from seed (in Minnesota), but if you manage your expectations, you don't necessarily have to look at those bare areas all season.
Spring Lawn Seeding: Manage Your Expectations
There are several factors that are going to affect the success of your spring lawn seeding. Spring is usually a time when our area receives regular rainfall. Because the seed bed needs to stay moist during the germination period of 2 - 3 weeks, this means that the homeowner doesn't have to work as hard to provide irrigation. On the other hand, when we do receive precipitation, it may be in the form of thunderstorms which can wash away freshly sown grass seed, especially if your seeding is on a slope.
(NOTE: Seeding on a slope should be secured with a mulch mat to help to hold seed and seedlings in place.)
Because you cannot do any weed control in newly seeded areas, you should expect to see weeds emerge along with your grass seedlings. In Minnesota, this means that you may have annual grasses, like crabgrass, compete with your desirable grass because you cannot apply pre-emergent herbicide. (This would prevent the germination of both the desirable and undesirable grasses and annual weeds.) Broadleaf weeds will also emerge and although the area can be treated after the new grass has matured, the weeds are going to outcompete the grass while they are there.
New turf that has been mowed three times should be mature enough to withstand some weed control measures. Broadleaf sprays will eliminate the most common weeds (dandelion, plantain, etc). If the population of annual grasses threatens to overcome your desirable grass, post-emergent sprays are available for those, too. After the control measures have done their work, your newly seeded areas may look bare but don't despair. One Kentucky Bluegrass plant, when in a suitable environment and properly maintained, can spread to cover the area of a dinner plate.
If you absolutely have to sow grass seed in the spring, manage your expectations. Expect to see weeds emerge and then expect to provide good cultural practices (mowing, watering, fertilization) in order to encourage the turf to spread.