Ask a Gardener – Watering New Trees

Friday July 29, 2016

How much water does a newly planted tree need in the hot summer of Colorado?

– Candice

With most watering questions, the not-very-satisfying answer is “it depends.” How much water your trees need can vary a lot depending on where they’re planted, what kind of soil they’re planted in, the amount of sunlight they get and other environmental factors.

Really the best way to make sure that your newly planted trees are getting enough water is to check the soil frequently and water accordingly. It’s almost always better to water new plants based on need rather than on a set schedule. Dig down into the soil a few inches. If the soil feels dry at that depth give the tree a good, long drink. If it still feels moist, let the soil drain and check back later. A moisture meter can also help determine if the soil is wet or dry.

Of course, that’s the ideal situation. But often, we just don’t have time (or, frankly, the inclination) to check the soil moisture levels several times a day, especially in the heat of the summer. But there are a few rules of thumb you can use to determine how much water your tree needs. Of course, these are just guidelines, but they’ll help you figure out a watering routine that works for you.

1. Water New Trees More Frequently – Newly planted trees need extra water and nutrients to help get established and they depend on you for nearly their entire water intake. Older tree with larger, more established root systems can access deeper groundwater and don’t need as much irrigation. As a general rule, it takes about 1 season per inch in trunk diameter to establish your tree. So, if your tree’s trunk is 2” in diameter, in will take about two growing seasons to get it established.

2. Water Deeper – Almost all plants do the best when they are watered deeply and infrequently. Shallow watering, even if it’s done every day, is usually not enough for trees and shrubs. Using a watering needle or a drip irrigation system allows water seep down deeper into the soil where the tree’s roots can access it. Many people also mound up dirt around the base of trees to form a little moat, preventing run off and allowing water to soak into the root ball.

3. Caliper Method – The CSU Extension Office offers these guidelines for establishing trees based on the caliper of the trunk. These are their suggestions for establishing trees with a trunk diameter of between 2” and 4”: – Daily for four weeks – Depending on temperature and wind, apply 1-2 gallons per inch of trunk diameter.

– Every other day for three months – Depending on temperature and wind, apply 2-4 gallons per inch of trunk diameter.

– Weekly until established (two to four or more seasons)

4. Root Ball Method – Watering according to the size of the root ball is another way to estimate how much water your trees will need. Give the tree enough water to equal to the size of the root ball at least two to three times a week. So, for example, if your trees came in 7 gallon buckets, give the tree 7 gallons of water three times a week. Apply the water slowly, allowing it to soak into the ground and saturate the root ball.

5. Winter Watering – Many newly planted trees get sufficient water during the growing season, but are then left high and dry during the winter. Some extra water between November and April can really help a new tree get established. For more info on this, check out our Fact Sheet.