Proper Summer Watering Of Trees
WHEN dry weather continues for an extended period, landscape trees depend on homeowners for water. It’s important to take care of surviving trees and nurture replacement trees with proper watering.
The amount of water a tree needs depends on many factors, including the age and species of the tree, the time of year, weather and soil type. As a rule, newly planted and young trees require more frequent watering than older, well-established trees. But during extended periods of drought, all trees benefit from supplemental watering.
Watering Newly Planted Trees
For the first several months after planting, most of a tree’s roots are still within the original root ball, with some roots beginning to grow beyond this area. The root ball and the surrounding soil should be kept evenly moist to encourage healthy root growth. After a few months, expand the watering zone to cover the entire area under the canopy. It can take two or more growing seasons for a tree to become established — for roots to venture into the soil well beyond the planting hole. It’s vital to provide supplemental moisture in those early years, if nature doesn’t provide regular soaking rains. During hot, dry weather, new trees may require water as often as three times per week to ensure that the root ball doesn’t dry out.
Watering Established Trees
It’s a common misconception that a tree’s roots are a mirror image of the above ground canopy. In reality, an established tree’s roots usually extend well beyond the edge of the canopy, or drip line. Although some anchor roots may reach deep into the soil, most tree roots are concentrated in the upper 12″ to 18″ of soil. When watering established trees, provide a deep, soaking irrigation to the entire area beneath the tree canopy and extending several feet beyond the drip line. Ideally, you should moisten the soil to a depth of 10″ each time you water. To prevent rot, don’t apply water to the area directly around the trunk.
Know When to Water
The easiest way to check soil moisture is to take a long (8″-plus) screwdriver and poke it into the soil. It will pass easily into moist soil, but be difficult to push into dry soil. If you can’t poke it in at least 6″, it’s time to water. This technique works best in clay and loam soils.
How to Apply Water
Overhead sprinklers are the easiest way to cover large expanses, but they’re inefficient, losing up to half the water to evaporation. Trees are better served by watering methods that apply water slowly, right at soil level. It may take several hours to properly water a single mature tree.
Frequently Asked Questions
How much water does my tree need?
As a general rule of thumb, apply an inch of sprinkler irrigation or enough water to moisten the soil to a depth of 10″ or more for mature trees. A common mistake is to apply frequent shallow waterings that don’t soak deeply into the soil.
My irrigation system waters my lawn regularly. Isn’t that enough for my trees?
Probably not. Most irrigation systems are programmed to apply frequent, shallow waterings. Trees do better with less frequent but deeper soakings — a heavy soaking once a week is much better than a shallow watering every few days. That’s because shallow waterings encourage tree roots to remain near the soil surface where they’re prone to drying out. Watering deeply, on the other hand, encourages deep, drought-tolerant roots.
Should I mulch under my trees?
Yes. Grass growing under trees will intercept much of the water you apply, keeping it from reaching plant roots. It’s best to keep a large (3′ plus), turf-free circle around the trunk. A 2″ to 3″ layer of organic mulch, such as shredded bark or pine straw, helps conserve moisture and keeps weeds at bay. To prevent rot, don’t pile mulch against the trunk.
Take Steps to Minimize Tree Stress During Drought
- Avoid digging under and around trees so you don’t disturb the roots
- Don’t do any heavy pruning. However, it’s OK to remove broken, dead, insect-infested or diseased branches.
- Keep an eye out for insect pests and disease, because drought-stressed trees are more vulnerable to attack.
- Avoid using high-nitrogen lawn fertilizers under trees, and never use weed-and-feed products, which can harm tree roots.