Keep our urban forest healthy by following these tree-watering tips

As the weather begins to heat up for the summer, it is important that trees are watered properly. The most recent city manager’s report emphasizes that regular, responsible watering can reduce the risk of drought stress—a condition that may not kill a tree outright, but will weaken its natural defense system so it is more susceptible to serious secondary insect and disease infestation.

With the Shot Hole Borer insect’s presence in the city, watering is essential. How much water a tree should receive depends on its size. As a general rule, the city’s arborists recommend approximately 10 gallons of water per inch of the trunk’s diameter for each watering. Using a hose at medium pressure will take approximately five minutes to produce 10 gallons of water.

The general formula for watering is: Tree diameter x 5 minutes = total watering time. It is essential to water throughout the entire canopy of the tree (the area beneath the tree from the trunk to the end of the branches).

Alternatively, the city recommends the use of a water bag at the base of a small or young tree to allow for a slow release of water over an extended period of time, which encourages deep watering.

Additional tree maintenance procedures that can significantly increase a tree’s chance of surviving through hot summer months include laying a three to four inch pile of mulch around trees to reduce moisture loss. Excessive mulching can suffocate a tree’s roots and can invite rodent pests (such as voles) and diseases.

Mulch should be pulled back at least six inches from the trunk of the tree. It is recommended to use wood chips, shredded bark, leaves or evergreen needles as mulch and to avoid the use of stone or rock near trees as this increases air temperatures and moisture loss. Fertilizers should not be used during hot summer months as salts in fertilizers may burn roots when there isn’t sufficient water. Fertilizers may also stimulate top growth resulting in too much leaf area in the plant for the root system to maintain during periods of low soil moisture.



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