The Grounds Guys
Sprinkler watering grass

How Much Water Do Your Trees Need?

As towering fixtures in our landscapes, trees are often ignored when it comes to their water needs. Watering trees typically takes a back seat to watering flower beds, but its importance shouldn't be overlooked. Trees are large plants, and they need sufficient water to maintain healthy growth.

The Grounds Guys® have seen many tree problems that are a result of drought stress. Unfortunately, symptoms of drought stress may not be evident for up to two years after a tree is deprived of enough water. By then, a tree's yellow leaves may not indicate a problem in the current season but drought stress from the previous year or two. This is why watering trees properly is essential to keep them in the peak of health.

Anatomy of a Tree's Root System

It's important to understand root structures and functions so you'll fully understand the basics of watering trees.

  • Did you know that most tree roots are in the top 18 inches of the soil, and 50 percent of the roots are located in the top 6 inches?
  • Most trees have roots that spread out far beyond the dripline, or outermost reach of the branches.
  • Typically, 50 percent of a tree's roots occur in the zone outside the dripline.
  • Some tree roots reach laterally the same distance as the height of the tree.
  • Newly planted landscape trees have roots that grow up to 3 times the spread of the branches (beyond the dripline) within the first three years.
  • The large, woody tree roots you may see protruding from the ground functional primarily as anchorage for the tree. Although they conduct water and minerals, the roots that actually absorb water are the much-smaller feeder roots.

How much water do trees need?

It depends on the size of the tree. A general rule of thumb is 10 gallons of water per inch of tree diameter.

  • Small Trees: up to 7 inches in diameter -- need up to 70 gallons of water (at each watering)
  • Medium Trees: 8 to 15 inches in diameter -- need from 80 to 150 gallons of water
  • Large Trees: 16+ inches in diameter -- need 160 gallons of water or more

How this translates to time spent watering trees:

Tree diameter x 5 minutes = time it takes you to water a tree. If you have large trees, time spent watering them with a garden hose is substantial. A tip from The Grounds Guys: As a time-friendly option, consider installing soaker hoses or a drip irrigation system.

How often should you water trees?

  • Newly transplanted trees need more water than established trees -- the first week, water every day; the next 4 to 6 weeks, water twice weekly.
  • Established trees may need water every 7-10 days during the summer months if there's insufficient rainfall.

Where should you water trees?

Look up. Walk until the outermost leaves are overhead -- this is the drip line. Now look toward the tree; you should water well within the drip line.

Watering Tips:

  • Prune trees properly. By leaving dying, insect-infested or diseased limbs on a tree, you can compromise its health, which weakens it during times of drought.
  • Mulch trees to help conserve water and suppress weeds that compete with the tree for water. Use 4 inches of organic mulch extended to the drip line but pulled back 6 inches around the tree trunk.
  • If you use an irrigation system for your lawn or garden, this helps with watering trees, too (if you use it properly).

Call on The Grounds Guys with all your tree questions -- put our experience to work for you!