Depending on the region of the country, supplemental watering may be an infrequent task or so regular that it requires an automatic irrigation system. The need for a good water supply to the plantings has been discussed in earlier chapters. Here the subject is the objectives of proper watering, its frequency, and its quantity.
Initially, watering must promote deep root development by the plant to establish it securely in its location. Later, watering must keep the plant healthy and growing actively even during dry summer weather. Much winter damage to evergreens can be avoided if the plants are kept well watered throughout the summer and autumn.
Not all plants require the same amounts of water. Neither will all plant root systems grow to the same depth in the soil. While nearly all landscape trees and shrubs will die if kept in either arid or water-logged soil for long, certain species are especially sensitive to sites that are too dry or too wet.
Infrequent and deep watering is preferable to frequent, shallow watering. Enough water should be applied to wet the soil to a depth of 12 to 16 inches. In the Southeast and Southwest, supplemental water may be required nearly every day. In other regions, supplemental watering may be weekly or even less frequent.