The optimum time to irrigate wisely is in the morning, with the cycle completing just before sunrise. This allows for the water to soak into the soil before evaporation begins with the heat of the day, while at the same time, minimizing the chance of disease.
Watering in the early evening increases the chance of diseases by maintaining a moist environment while temperatures are low (especially during the spring and fall seasons), but this can be minimized by not overwatering.
Water during the heat of the day is not recommended because of excessive evaporation of water due to temperature, wind and humidity; 20 to 30 percent of the sprayed water could be lost. Also, on the very hottest days, applying water to plants could cause scalding and leave your plants stressed.
As the optimum time to water is sometime early morning, an automated system is your best bet.
