During periods without rainfall, trees should be thoroughly watered on a regular schedule.
Slow watering provides a cool drink for thirsty trees and creates a water reserve, much like filling up a sponge. Tree roots draw from the reserve until the next watering session. This encourages development of deeper roots and keeps trees happier during hot dry summer days.
Urban landscapes often have compacted soils which can lead to shallow root systems as trees seek out moisture closer to the surface. We suggest using a deep root watering probe that connects to your garden hose to deliver water directly to the tree’s root zone.
Start 3-6 feet from the base of the trunk and push the tool 6-12 inches into the ground to get below the surface compaction layer. Turn the water on low and let it run for 15-20 minutes. Then, move the probe to a second location (1-2 big steps) within the drip line of the tree - the area between the edge of the foliage and the tree trunk. For small trees up to 12 inches diameter, water in 3-4 locations around the tree. Increase the number of locations for larger trees.
Another useful tool for young trees is a watering bag that can be refilled with a hose.
You can also water your trees with just a hose. Set to low flow (just above a trickle) and thoroughly saturate the soil. It is important to run the water long and slow to avoid run-off and evaporation.
Trees For Seattle recommends that newly planted young trees need 15-20 gallons of water twice per week. Mature trees should get a good soaking one or two times per month. Adding a layer or arborist chips or mulch around your trees will help conserve soil moisture.
Do you have questions about when and how much to water your trees? Contact the Certified Arborists at Tree133.