When the dog days of summer are in full swing, heat can send people seeking relief in air-conditioned buildings or under a tree’s shade.
Surprisingly, though, trees need help cooling down and recovering from the excessive summer heat, too. Well-hydrated trees cope better with the summer’s scorching heat and parched soil.
But how much water do they need? And when is the right time to water them?
Most trees are sufficiently hydrated if the upper 12 inches of soil around the tree’s roots are soaked at least once per week. The rule of thumb is generally five gallons of water for every inch of trunk diameter. Be sure to concentrate on the “drip zone,” which is the area directly beneath the tree's foliage.
To ensure the tree is getting just the right amount of water, follow these easy tips from RJ Laverne, an International Society of Arboriculture Certified Master Arborist® at The Davey Tree Expert Company. Plus, Laverne shares the symptoms to look for if the tree needs more or less water. The signs are easy to read and will ensure optimal tree health throughout the summer’s heat.
Tips for Perfect Tree Watering
- The best time to water is in the morning. Run a sprinkler beneath the tree as slowly as possible, use a drip hose, or just apply a slow trickle from a garden hose. Avoid directly irrigating the trunk of the tree, as increased moisture can create root rot.
- Tree roots are deeper than turf roots, so water about three times as long as you water your lawn to make sure enough moisture reaches the root zone. If the soil is adequately saturated, you should be able to easily insert a long screwdriver 6 to 8 inches into the ground.
- Place a coffee or soup can in the “drip zone” and run the sprinkler slowly until two inches of water has collected in the can.
- “Do not pile mulch around the base of your tree, a condition we arborists refer to as 'mulch volcanoes,'” warns RJ Laverne. “Thick piles of mulch can reduce water and air infiltration into the soil, which can create an unwanted environment for decay organisms to attack the base of the tree.”
- Instead, it’s much better to apply a broad ring of mulch about 2 to 3 inches deep that does not touch the base of the tree, advises Laverne. “Mulch donuts are better than mulch volcanoes.” To achieve this, pull mulch back 6 inches from the trunk of the tree in a saucer-like fashion.
- Feed trees with fertilizer annually to keep them nourished throughout summer’s high temperatures.
Signs of Under-Watering
- Wilted, drooping or curling leaves that may turn brown at the tips or edge
- A sparse canopy of off-color and undersized leaves, leaf scorch or yellowing
- Untimely fall color and early leaf drop
Symptoms of Over-Watering
- The area around the tree is constantly wet
- New growth withers before it’s fully grown
- Leaves appear green but are fragile and break easily
Fool-Proof Water Check
Still a bit uncertain about the right amount of water? The soil around a tree’s roots tells a story.
Grab a shovel, dig down about 6 to 8 inches and pick up a handful of the soil. It should be cool to the touch and slightly wet—but not soaking. If the soil is really wet, it’s a sign of over-watering, so cut back for a bit.
Now, if you don’t have sandy soil, roll the soil into a ball. If it doesn’t hold its shape, the soil is too dry, and it’s time to amp up the watering.
Following these watering guidelines will ensure trees survive the sizzling summer heat and can continue being the most valuable asset in the landscape. When watering, always follow local irrigation ordinances. Questions? Find a local, certified tree care specialist at Davey Tree.