Mow your new lawn when over 50% of it reaches a height of 4-5”.
Mow lawn to approximately 4” high. Never remove more than 1/4 of the length of the grass per mowing. Do not expect your lawn to look like established turf at 30 days. It may be quite sparse. If it looks like a lawn from a distance it should be fine. The grasses will thatch together and thicken up each time you mow. You will have to mow 5-7 times before the lawn will look lush and thick. At least for the first 5-7 times of mowing, use a grass catcher when you mow.
* Sharpen Lawn Mower Blades
* Thoroughly wash mower prior to mowing new lawn to help reduce any possibility of spreading weed seeds, fungal spores, and other potential diseases.
Small bare areas are usually caused from seed drying out or being flooded and washed away. These areas will have to be hand seeded to introduce new seedlings for growth.