Amount
Watering enough to get into the root ball or root area 6” to 9” down, once a week is ideal. All depends on the size of tree, soil conditions, weather conditions, and type of plant. Check soil with a trowel 6” down or by the finger test.
10 gallons of water per 1” of trunk, 10 to 15 gals. a week, depending on rain. 1” of rain equals 4.7 gallons of water per sq. Yard. So, a 2 to 3” rain will give a tree 9.4 to 14.1 gallons of water.
Established trees can be watered every 10 to 14 days during dry periods or drought in and around the drip zone of the tree.
Newly planted trees should be checked daily at first to observe how quickly the soil dries out and how mulch and environment is a factor. Once that is determined check weekly. Water, when needed as the top 6 to 9 inches of soil dries, usually once a week. Remember all the roots are in the root ball until the roots establish in the following 2 to 3 years.
Many options for watering:
By hand with hose nozzle or bucket, waterbag, root feeder, irrigation system, soaker hose. Whichever option works for you, remember to check the soil and the signs of the plant before watering.
Shrubs should be checked weekly and watered slowly to ensure water is absorbed into the soil. Newly planted shrubs may be watered more frequently than once a week but always with a deep watering. Deep infrequent watering equals deep roots. Frequent watering results in shallow roots. Never water newly planted plants every day.
It is important to water roots not the leaves.
In the Chicago environment, regular water till the end of October with watering when needed in November. Do a final deep watering of all plants at the end of November to ensure moisture in the soil so plants do not dehydrate during winter. If there is a dry winter with no snow or little rain, then water on a warmer 40 degree day in January or February.
