Tree roots are not like carrots. Tree root systems can spread two to three times wider than the height of the tree. Most of the tree’s absorbing roots are in the top 12" of the soil. Water should be applied within the drip-line (the critical root zone in the box above).
Water deeply and slowly. Apply water so it moistens the critical root zone to a depth of 12". Methods for watering include a deep root fork or needle, soaker hose, or soft spray wand. Apply water to many locations under drip-line. If a deep root fork or needle is used, insert the device no deeper than eight" into the soil.
How much water should I apply? As a general survival rule, apply 10 gallons of water for each diameter inch of the tree. For example, a two-inch diameter tree will need 20 gallons per watering. Use a ruler to measure your tree’s diameter.
When should I water? Fall and winter watering, October – March, one to two times per month, depending on weather, temperature and soil conditions. Never water trees when the temperature is below 40 degrees or if there is snow cover. Spring and summer watering, April – September, three times per month, depending on weather and watering restrictions.
Mulch helps conserve soil moisture. Apply organic mulch within the drip-line, at a depth of four". Leave a six-inch space between the mulch and trunk of trees. Mulch materials may include wood chips, bark, leaves and evergreen needles.
Consistent moisture is needed. Drought-stressed trees are more vulnerable to disease and insect infestations and branch dieback. Keep a watchful eye for anything that looks out of the ordinary.
Use this chart for specific information on watering devices, duration, and amount of water needed.