Watering plants properly from day 1 is the best way to increase their chances of surviving past the first growing season.
Here are some tips on how to do just that.
1.
Create a berm just outside of the planting hole that will retain water long enough to soak the root ball of the plant (often times the back fill soil will saturate much more quickly than the root ball itself, leaving the root ball relatively dry).
2.
Heavily water your tree or shrub prior to, immediately after, and the day after planting date. This insures all voids between the root ball and ground will be filled. Having too much air contacting the roots can stress plants.
3.
Maintain a watering schedule. Water twice a week (three times a week in +95 degree weather) for the first month (when there is less than an inch of rain per week). Ideally a 5 gallon bucket with a few holes poked in the bottom and sides should be sufficient for large trees and shrubs. The slow release will allow for the water to soak in before it becomes runoff travelling away from the root ball.
4.
After the first month, 10 gallons (add 10 gallons per inch of diameter for trees greater than 2") once a week will percolate deeper into the soil, coaxing a deeper root system. Smaller trees may require less amounts of water, but be sure the root ball is thoroughly saturated. During excessively hot weather (95+), go ahead and water twice a week as the soil begins to dry out much more quickly.
5.
Don't neglect your plants during the winter! Just because they drop their leaves doesn't mean they don't get thirsty. During winter months, however, watering amounts should be reduced by half as long as the ground isn't frozen. Shorter, cooler days make plants require less moisture. Make sure the ground isn't frozen, and a mild temperature is forecasted for the next 2-3 days that won't freeze the ground deep enough to harm the roots. Winter rules especially apply to evergreens. Because evergreens maintain their leaves, they lose more water moisture than deciduous trees and shrubs.
6.
During the second and third growing seasons after planting, continue to water trees and shrubs every 10-14 days if it doesn't rain and soil moisture indicates the need to water. As the root system of these plants extends during establishment, water in a wider ring around the plants, soaking the soil to a depth of 8 to 12 inches.
7.
Turf grass growing over the root system of young trees competes for moisture. To reduce competition, maintain a grass-free area around the base of the young tree, extending to the drip line of the outer branches or beyond.
8.
An organic mulch around the base of young trees and shrubs is recommended to keep the soil moisture more uniform and to stabilize soil temperature. Apply and maintain an organic mulch ring 2 to 3 inches deep around the base of the tree, covering the grass-free area.