Summer Tree Watering: Measurable Tips For When & How Much



It’s hot and dry and you suspect your client’s trees need watering. But how do you know for sure, and how much water is needed? After all, overwatering isn’t healthy either. So how do you make an informed plan for those without irrigation systems? The Arbor Day Foundation offers these simple and measurable tips.

The Screwdriver Test. There’s a simple step you can take to see if a tree needs water. Using a long screwdriver with a minimum six-inch blade, probe into the ground in several locations under the drip line (the furthest edge of the tree’s canopy). If you are having difficulty probing to a six to eight-inch depth and natural rainfall is not in the forecast, then you should begin a watering regime, or inform clients of the necessity.

The Bucket Test. Typically, a garden hose running at a moderate rate will disperse 5 to 10 gallons of water per minute. This is an important thing to know about a client’s hose — so test it. Using a five-gallon bucket, time how long it takes the hose to fill it up. Knowing the hose’s flow rate will help you make informed decisions regarding watering duration for the property’s trees, as the general rule of thumb is to give the tree around 10 gallons of water per inch of trunk diameter.

Young Trees. As you know, new trees, or those planted within the last two years that have trunks less than one inch in diameter, require more frequent watering. Inform clients to aim for two to three times per week, watering the tree for about one minute to ensure a deep soaking. They should keep the water flow at a moderate level. Or ideally, install a slow-release tree watering bag around new or young trees. This type of system can save time for you and your clients and really adds up when you’re caring for multiple trees!

Older Trees. Established trees, or those two years and older, usually don’t need to be watered quite as often. Aim for once a week or every other week, depending on how the soil is retaining moisture. During unusually dry periods, these trees should receive a deep soaking to stay healthy. A common mistake with established trees is to give them shallow watering doses focused at the base of the tree. Avoid this by using a soaker hose in a spiral pattern extending out to the tree’s drip line. A long period (four hours or more) using a soaker hose will properly water the entire root system of the tree.

Pete Smith is an ISA-Certified Arborist with the Arbor Day Foundation. An original version of this article appeared on the Arbor Day Foundation Blog.

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