The best time to water grass, like so many things in life is dependent on circumstances. For established lawns the best time of day to water grass is in the early morning hours, preferably just before sunrise. This enables the water to soak through the soil and completely nourish the plant’s root system. Watering in the morning also minimizes the loss of moisture due to the higher temperatures during daylight hours and takes advantage of the normal morning calm from wind that may cause water to drift away from the target area. Evaporation is also minimized and morning watering enables the homeowner to take advantage of the effects of morning dew that already exists on grass blades. The natural ground shade afforded by the grass will enable the soil to dry out slowly throughout the day. Without an automatic sprinkler system this early morning watering may present a challenge. The point is that the earlier one waters, the better it is for the lawn. Under all circumstances, watering in the evenings should be avoided. Evening watering causes the ground to remain moist and gives rise to a number of diseases that will weaken root systems and cause premature browning or even loss of plants. Perhaps the most prevalent example of available to most home owners of good turf maintenance is demonstrated by the grounds keepers on golf courses throughout the country. They have immense sums of money invested in maintaining healthy turf and one can readily note that they water their established turf exclusively in the morning.
There is always an exception to the rule and certainly there is one for those that are just beginning to establish a lawn or have areas where seeding is being done. Under these circumstances it is preferable to water newly seeded areas several times a day for best results. Seedlings need to remain moist for germination to occur. It is critical to keep the seeds or early sprouts moist. One should attempt to control “puddling” as it will often cause seeds to wash away and result in bare spots. Additionally, the goal is to keep the seeds moist and it will waste water to apply too much.
The objective of water established lawns is to insure the water is available for the root systems , while the objective of watering newly seeded areas is to keep the seed moist. Therefor a considerable less quantity of water should be used for newly seeded areas.