Sod, though more expensive than seed or plugs, creates a lawn that is instantly attractive and able to tolerate foot traffic much faster than seeded lawns. Excellent care of the newly laid sod protects your investment of money and effort. Knowing approximately when roots should start to grow into the underlying soil and how to check for this growth allows you to gauge your level of success and adjust your care routine when the sod has rooted accordingly.
New sod will typically begins to send roots into the soil within days after it is laid and is typically attached well enough to the soil to be considered "rooted" beginning about one to three weeks after installation. Extremely hot or cold weather and improper moisture levels can slow sod root growth. If the sod was laid while the grass was dormant in fall or winter, it will not root until growth resumes in spring. Poor installation practices, like letting the sod sit for too long on pallets before laying it or leaving gaps between sod pieces, can also cause slow root growth.
Testing for Root Growth
The best way to determine if the sod has rooted in the underlying soil, or knitted to the soil, is to physically check for root growth. To do this, gently try to lift up a corner of a section of sod. The amount of resistance indicates the extent of root growth. If no root growth has occurred, the corner of the sod will lift easily, while a completely knitted piece will be difficult to lift. Checking several different pieces in various parts of the new lawn will help to give you a good understanding of how extensive the rooting is and if you need to adjust care practices in any areas of the lawn.
To encourage sod root growth, you need to keep the underlying soil constantly moist but not soaking wet. This means watering the sod lightly every two to three days, wetting the sod and moistening just the top 1 to 2 inches of soil. During hot, dry weather the sod may require daily watering. Once the sod has rooted, increase the amount of water supplied at each watering session and decrease the frequency. Each watering session should moisten the soil to a depth of 4 to 6 inches.
Other Sod Considerations
Lightly rolling the new sod in shortly after laying it and as soon as the turf is dry enough to walk on following a thorough soaking at installation forces the sod roots into contact with the underlying soil. Limiting traffic on the new sod lawn to that required to care for the lawn will also help to ensure rapid root growth.