It will be necessary to water all perennials, ground covers, trees and shrubs heavily every 5-7 days for the first month after installation. Do not depend on rainfall to provide an adequate amount of moisture.
Water new trees and shrubs deeper and less frequently. You should be able to apply 10-30 gallons of water once a week, depending on plant/root ball size. Apply the water slowly enough that the soil will absorb it and have as little run-off as possible. Once established, trees and shrubs should require only supplemental watering during extended periods of hot, dry weather.
Water ground covers thoroughly immediately after planting, and continue frequent watering until the plants are established. Water the beds deeply. Shallow watering encourages shallow root growth that is easily damaged during dry periods.
Perennials generally need an inch of water per week during the growing season. More may be required during bloom or during the hot summer months. Supplemental watering should occur during the morning hours. Avoid watering of foliage or flowers.
Water new grass seed often in order to keep it and the top 1/4" of soil constantly moist, approximately 15 minutes per area. In hot, dry or windy conditions, you may need to water frequently in short durations. It may be necessary to water several times a day. In cool, wet or calm conditions, additional water may not be necessary.
After germination - once grass has emerged - reduce the frequency of watering, but water for longer periods of time (approximately 2 hours per location) to allow for better root development. Allow time between watering for moderate drying. Lawn can be mowed to a 2 1/2" height once it reaches 3 1/4". Never remove more than 1/3 of the blade in any single mowing.
If you have new sod, water every day for the first 6 days, then every other day for the next 6 days. Check the root system to see if it is ready for mowing. Watering should be heavy - approximately 2 hours per location - paying particular attention to edges. Never allow standing water. You may have to water more frequently the 2nd week and extend the watering in case of hot, dry and/or windy conditions.