All seeds require moisture and a certain temperature range before they begin to germinate. Once the germination process has begun, if conditions change, the seed or new sprout is vulnerable and can die.
If the seed or sprout dries out, it dies out. Your mission then, is to provide adequate moisture at all times. The pre-sprout phase is most critical. Your commitment to watering new grass seed must stay strong. The germination time for grass seed ranges from 5 to 30 days depending on the variety. It can be even longer than this in cooler temperatures.
This is how long it will take to actually see the grass growing. Until this point, the seed, or the soil and mulch in contact with the seed, must stay moist. It doesn’t need to be soggy or swimming, but moist.
Once the new grass is visible, the roots are also growing down into the soil. This happens quite quickly. As soil moisture below ground is more accessible to the roots, the plant is not so vulnerable now. However, don’t reduce the amount of watering on new grass seeds yet.
Seeds will not sprout all at the same time. Seeds will be buried at different depths, absorb water differently, or be of different quality or maturity. Many seed mixtures are blends that will have different characteristics affecting their development. It is important to keep the surface level of soil constantly moist until all seeds have germinated.
Until the planted area is densely showing green growth, don’t allow it to dry out. The percentage of seed germination is in your control, though people often blame a thin lawn on the “lousy seed that didn’t come up” It is possible to increase the percentage of germinating seeds.
Existing Lawn Being Over-seeded
Normally a lawn should be watered deeply but infrequently. Change this when you are watering for new grass seed. Now you must water every day. Set automatic timers for about 5 to 10 minutes early in the morning and again at mid-day. Observe and adjust this time. Sprinklers have a broad range of flow in gallons per minute and you must use your judgment here.
Watering done by hand or hose-end sprinklers must be consistently and evenly applied. It should provide approximately the same amount of moisture throughout, but less in shady areas.
Twice daily watering is essential until the new grass is up, then after one more week, reduce to once per day. Adjust this pattern according to season and temperature demands.
Bare Lawn Areas Being Filled In
If there are areas of substantial size or number, follow the same instructions as above. For smaller amounts or areas, if hand watering is practical, leave the lawn on its normal irrigation schedule. Supplement the bare areas twice daily, or as needed, to keep the new seed moist.