Proper watering is extremely important to ensure success at growing plants in the home landscape.
Soil depth affects water availability to the plant. Soils that are several feet deep will serve as larger reservoirs for water than will shallow soils. However, plants must have a root system that is able to access the deeper soils. Trees, shrubs, and most perennials will easily send roots down to 3-4 feet while annual plants tend to be more shallow rooted. Deep rooted plants can go longer between watering than those with shallow roots.
A thorough soaking once a week during the summer months is usually sufficient for trees and shrubs while annuals and other shallow rooted plants may require watering every 2-3 days. Newly planted plants should be watered more frequently since their root systems are less established.
The question arises, how much water should I apply to my plants? Think of this in terms of how much water it takes to satisfy you on a hot day. A splash to the face is refreshing but usually only satisfies us for a short time, and is never meant to be our sole source of water. A similar dousing of plants on a hot day with a hose is rarely sufficient to supply the needed water. Such watering rarely penetrates more than an inch or so into the soil.
A thorough deep watering is much more effective. Apply water to the base of the plant and use a hose attachment to help break the water into finer droplets and allow it to more easily soak into the soil. Apply water for several minutes before moving the hose to the next area.
Such watering will encourage plants to develop deep and well dispersed root systems that provide good anchorage and help them obtain water more effectively during drought.
Another question is, what time of day should water? The morning is the best time to water plants in the landscape. Morning watering gives wet foliage a chance to dry fairly rapidly while evening watering tends to result in foliage that remains wet throughout the night. Foliage that stays wet for several hours has a much higher incidence of disease.
However, watering in the evening is better than no water at all just ensure that the water is directed at the plant base and away from the foliage. Watering during mid day is not recommended because rapid evaporation of water from a plantís leaves may concentrate salts and burn the foliage.
Remember, for healthy plants in the landscape, morning is the best time to water, and occasional thorough watering once or twice a week is preferred over daily light watering that only wets the surface of the soil.