How Much Water Do Trees Need?

Mar 27

Research your Trees

Many factors determine how much water the trees in your landscape require to thrive. This post includes industry-accepted amounts, frequency, and techniques. However, it is encouraged for tree owners to research or seek assistance in determining tree species requirements, soil type and condition, and site stressors that could influence the ideal watering of your trees. Lack of watering in drought conditions as well as Over-watering will stress your trees so it is important to monitor your soil and any response the tree might have to your efforts. If planning a landscape, consider looking for native or drought-tolerant species for sites that will have difficult watering access.

How Much? How Often?

The general rule for watering young trees is 10 gallons per inch of trunk diameter each week during the growing season. Newly transplanted trees could use this number every day for a week, then every 3-5 days to help with transplant shock. As a tree matures and grows a more vast root system, this watering requirement can decrease. Still, it will be important to monitor the moisture level of your soil throughout the dripline of the tree and continue irrigating if needed. During the winter months when a tree is dormant, it should still receive water once a month; try to find days when the air and surface temperatures are above 40 degrees Fahrenheit with no snow on the ground.

Methods

The best method for watering trees is with a slow enough flow that the water soaks into the soil throughout the tree’s dripline (canopy) instead of experiencing surface runoff. The goal is to get the top 12” of soil within the tree’s drip line, which is an estimate for the root system expanse, to a moist level. Feel free to use a hand trowel to excavate some soil where you have watered to assess the effectiveness of irrigation.

Using a hand feel test, those levels would be: Dry and Crumbly, Moist and Malleable, Soggy and Runny

The tree owner needs to adapt irrigation methods that fit the site, soil type, and personal available effort. Remember to try and spread the required volume throughout the dripline, not just at the base of the tree trunk. If possible, it is best to water in the mornings so that water is available to the roots when the trees begin transpiration in the heat of the day.

Site Improvements

Reducing competing plants within the dripline of the tree ensures that the water provided is going to the tree instead of weeds, turf grass, or plantings. Deep soaking can help get water available below any shallow roots of competition. Mulch circles can be an attractive alternative ground cover and provide many benefits to trees. A 2-4 inch layer of mulch helps retain surface moisture, regulates soil temperature, suppresses competing plants, reduces mechanical damage from mowing, and decomposes over time to provide nutrients. If mulch is applied, keep it off the root collar (base of the trunk).

Monitor the compaction of the soil around the tree. A compact soil will not allow water to penetrate and is very detrimental to roots, which require air pores in the soil to thrive. It is best to prevent compaction within the dripline of the tree but there are methods available to help with aeration.

Reach Out

If you need the help of an arborist to assess your tree, soil, and site or provide guidance on your watering efforts. Please feel free to reach out to Northeast Tree Care and look at other services related to Plant Health Care.

Joe Boerner