Plant health & long life can be achieved by exercising the proper care right after planting & through their lifespan.
A few long and deep waterings every week are better than more frequent light waterings. The best way to determine if watering is needed, is to remove some mulch from around the plant and check the soil. It needs to be moist (not crumbly/dry; not swampy/muddy). The soil should be allowed some time to drain between watering in order to promote air penetration into the soil (for good root development).
During the summer months, watering four times per week is required. Plants may be watered less during cool and wet weeks. Do not rely solely on rainfall and do not water when temperature is below freezing at night. While watering, water needs to be directed towards the base of the plants (over the root area). The perfect time for watering is early in the morning before the sun becomes strong.
Larger size trees need approx. 15 gallons, medium size shrubs need approx. 5 gallons, & smaller plantings need approx. 1 gallon. These are rough quantities & exact amount of water varies. Watering should be tailored for each plant based on its type & size. Automated soaker hoses, and micro spray nozzles are the ideal and most efficient way to water your garden.
Mulch around your plant helps even out moisture and temperature fluctuations. A good layer of mulch (1-2") should be maintained around your plant. Mulch also helps suppress weed growth and adds organic matter to your soil as it decomposes. Proper pruning is key to keeping the desired shape and size of your plant. All dead branches/stems should be cut back. Plants should receive routine fertilizer treatments to help supplement nutrients that are not always present in the native soil.