Watering New Trees

New trees are an investment, plain and simple. Not only are they an investment of money but an investment of time and labor too.

As we approach the hottest and driest time of the year here in Southern Idaho, proper irrigation of our newly planted material is crucial. The hard part is knowing how often and how much to water. I wrote this post to help give you the tools necessary to carry your trees through this summer's heat and beyond.

The first thing to understand is that trees and shrubs are very different from turf grass. Grass has shallow roots and likes a little water, frequently. Trees, have deeper root systems and like a lot of water infrequently. Sprinkler systems will never provide sufficient water to trees!

Watering Frequency

After planting a tree, the frequency at which you water is important. Here is a good guide according to the University of Minnesota.**

  • 1-2 weeks after planting, water daily.
  • 3-12 weeks after planting, water 3 times a week.
  • 12 weeks and beyond, water weekly until established.

**The soil and climate varies greatly in Idaho compared to Minnesota. This is a great starting point. Your tree may need more frequent watering depending on elevation and soil structure.

Watering Amount

Larger trees will need more water at these intervals than smaller trees. One of the benefits to planting smaller trees is less need for water and a shorter establishment time. Here is a guide to help you know roughly how much water your tree will need at the needed intervals according to the tree's caliper (diameter of the trunk 6-12 inches above the soil).**

  • 0.5 - 1'' caliper - 3-5 gallons
  • 1.5 - 2'' caliper - 6-10 gallons
  • 2 - 3'' caliper - 12 - 20 gallons

**Soil structure varies greatly across Idaho. Your soil may hold more or less water than this. We strongly suggest building a "bowl" or watering basin around the tree to collect water. How fast/slow the water drains will inform you of how much or little water you will need.

As stated earlier, larger trees will take longer to establish. According to the University of Minnesota, the amount of time a tree takes to establish is as follows:

  • 0.5 - 1'' Caliper ~1.5 years
  • 1.5 - 2'' Caliper ~3 years
  • 2 - 3'' Caliper ~5 years

Other Tips

  • Build a basin around the tree to collect water, don't let the water simply wash away.
  • A slow trickle from a hose or drip system works great. it allows the tree to slowly take up all the water. You can time how long it takes to fill the basin, to establish your watering regimen.
  • 2-3'' of mulch around the tree's root zone will help keep in moisture. Bark keeps the soil cool, reducing evaporation and reduces competition with turf.
    • Turf will always out compete your tree for resources, specifically water.
    • Do not pile up bark near the base of the trunk.
  • We strongly suggest not using rock at the base of the tree until it is established.

A newly planted tree with a proper sized mulch zone and watering basin. Photo courtesy University of Minnesota Extension.

If you have any questions feel free to comment below on contact us!

Source:

  • Zuzek, K. 2018. Watering newly planted trees and shrubs. University of Minnesota Extension. https://extension.umn.edu/planting-and-growing-guides/watering-newly-planted-trees-and-shrubs

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