Deep Watering Trees

Young Trees

• For the first three years, young trees need slow, deep watering during the dry season. This is usually from April to October but may be longer.
• Water deeply by setting your hose on a slow trickle or using a soaker hose near the base of the tree. Leave the hose on trickle for about 2 hours. 
• On average, your tree will need 15 gallons of water per week.
• Water two to three times per week depending on how hot and dry it is outside.
• Remember that watering your lawn will not replace the need to deeply water young trees. Deep water encourages roots to grow down. Sprinklers leave water on the surface and encourage roots to grow along the surface - causing problems in the future.

Soil Tips:

Check for Moisture: 

Before watering, check your soil to see if the tree needs more water. Probe the soil near the root ball 8-12 inches below the surface. A screwdriver can be handy for this. If the soil feels moist and sticky, allow it to dry for several more days before watering again. If the soil feels dry and crumbly, water deeply. 

Check for Drainage:

To determine how well your soil drains, dig an 18-inch hole about one foot deep (width does not matter). Fill the hole with water and let it drain out all day and overnight. Fill the hole to the top with water the next day. Place a stick in the center of the hole and mark the water level on the stick. Mark the stick again after 30 minutes and then again, each hour to measure the water level.

Poorly drained soil will drain about one-half inch per hour. Moderately draining soil will drain ½ to 1 inch per hour. In soil that is well drained, water will recede 1 inch or more per hour.

Mature Trees

• The best way to deep water trees is to use a soaker hose that slowly applies water to the soil over several hours. Sprinklers may be used to water deeply by watering until water begins to run off, then waiting at least an hour or two to resume watering. This should be repeated until water has penetrated at least two to three feet in depth.
• Special care needs to be taken when watering on a slope. Water around and beyond the dripline of mature trees where the roots are, not near the base of the trunk.
• Watering during our rainless months varies greatly depending on the tree species, daily temperatures, and location in the yard, as well as soil texture, structure and depth. 
• Use a shovel or soil sampling tube to check the depth of moisture to at least a foot.
• Established drought tolerant trees may need occasional watering at one- or two-month intervals. California native oaks, California laurel, cork oak, Chinese Pistache and Goldenrain trees can be damaged and short lived with frequent summer watering.
• Moisture adapted trees such as birches, redwoods, magnolias and red maples may need regular deep watering throughout their lives to look their best and perform well. These and other species greatly benefit from an occasional deep watering to the depth of at least a foot once or twice a month.
• Trees in or near lawn areas with frequent shallow watering may develop surface roots.
• Poorly adapted Monterey pine, Leyland cypress and giant sequoia are prone to insect damage and diseases in hot dry interior areas regardless of how much water they are given.