Most people water their lawns and flower beds from above, using a sprinkler device, or a hand-held hose, or watering can of some sort. For lawns and landscapes with few plants other than trees and shrubs it is the easiest way to water. There are several considerations when watering from above and they should be evaluated in selecting watering devices. When you water with an overhead sprinkling device, for example, you lose about 30 percent of the water to evaporation and runoff. If you use mulch in your yard as you should, then when you water from above you inevitably must use additional water to moisten the mulch each time (water has to penetrate the mulch before it can reach the soil).
Overhead watering can be a problem for another reason. It can encourage disease in your landscape plantings if not used properly. Since the leaves of the plants get wet, certain fungi and other disease spores are encouraged to multiply. If you can avoid wetting the leaves every time you water, you will definitely reduce the danger of certain diseases like mildew and black spot.
Overhead Watering Principles
For people who use conventional overhead watering methods, here are some good watering principles to follow.
1. First, always water deeply so that the soil is moistened at least 8 to 12 inches down. Observe the guideline of about an inch of water a week, preferably divided into three sessions. Even with the evaporation and runoff, one inch a week should serve the needs of most plants on your property.
2. If possible, water in the morning, so foliage has a chance to dry.
3. And last, avoid watering at midday, because that is when loss to evaporation is greatest.