Irrigate, irrigate, irrigate, but don’t create a swimming pool
Keep the seed bed watered as often as necessary to keep the top half-inch of soil constantly moist, but don’t create pools of standing water or let it dry out. In May, this may only be twice a day and in June, it will probably be three times per day. It is critical to not let the seed bed dry out between watering cycles because Bluegrass will not germinate under these conditions and annual weeds love said conditions. If you did a good job watering, you should have a full stand of grass at the end of 3 weeks. Now you can begin to cut back the applications per day and water longer, but don’t water late into the evening because fungai love damp, warm growing conditions and it can kill a lawn faster than you can establish it. l
Between 3 and 4 weeks after seeding, it is time to apply a starter fertilizer. A good formula should be about 22-10-8, but most of the nitrogen should be slow release and a middle number of at least 10. This fertilizer application is very important because of it increases the density of the turf and reduces the ability of weeds to establish, (You will always have some weeds, but they will be easy to control if you follow this program). A follow-up application of the same fertilizer about 5 weeks later is necessary to develop a good root system.
Don’t forget to mow your new lawn! Your lawn is ready to mow anytime the leaf blades reach 4 inches. Mowing promotes tillering and speeds the establishment of your lawn, but only remove a 1/3 of the grass blade at a time. Cutting to short can hurt the young grass plants. During the first year don’t mow your lawn shorter than 3″ to maintain a healthy lawn and prevent stress. Other rules: Don’t mow after watering or early morning with heavy dew. Avoid bagging clippings regularly because you are removing key nutrients from your lawn.
Most weed control products will be safe to use on your new lawn 8 weeks after germination provided most of the seed had germinated in 3 weeks and you were mowing after 3 weeks. Remember, it is much more important to get the lawn established before killing weeds. Experienced lawn care companies can easily control the weeds if the lawn is healthy. If you are doing the spraying yourself, use the low application rate on the container the first time.