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.
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. Until you see a grass sprout, it is important for the seed, soil or mulch to stay 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 vulnerable now. But don’t reduce the amount of water just yet.
Related: Caring For New Sod
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 of multiple varieties that will have different characteristics affecting their development. It is important to keep the surface area constantly moist until all seeds have germinated.
Until the planted area is densely showing green growth, don’t allow it to dry out.
How much to water?
The requirements for watering new grass seed can be altered for each of the following circumstances.
An existing lawn being over-seeded.
You must water every day. If you have a sprinkler system set automatic timers for about 5 to 10 minutes, early in the morning, and again at mid-day. Make sure you adjust the time accordingly, all sprinkler systems are different!
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 the season and temperature demands.
Bare lawn areas being patched.
If a lawn area is of substantial size or you have multiple areas, follow the same instructions as above.
For smaller amounts or areas, if hand watering is practical, leave the lawn on its normal irrigation schedule for a single cycle each day. Supplement the bare areas once or twice daily, or as needed, to keep the new seed moist.
New lawn areas sowed with grass seed.
New lawn preparation done properly will have tilled the soil to loosen the ground for the new grass plants. This loose soil is prone to holding large amounts of water. DO NOT OVER-WATER!
The top inch of soil should stay moist at all times. This may take only 2-3 minutes or 5-6 minutes, or longer, depending on your sprinkler system and the soil type. Use your best judgment, moist but not soggy is the plan!
As above, it should be repeated 2 or even 3 times each day is appropriate if the weather is hot enough to require it. Watering new grass seed on new lawn areas do NOT require lengthy watering times. That simply sends the water deeper than it is needed at this early stage.
Frequent watering is the only way to keep adequate surface moisture.
Related: Tips for Proper Watering
Problems to Avoid When Watering New Grass Seed
- Over-watering that results in puddles
- Run-off and seed movement on sloping ground
- Over-watering that leaves the soil soggy and spongy
- Over-watering areas that are shaded
- Uneven watering