Watering Mature Trees
Summertime Watering Tips – Part 2 of 3
Our urban forest provides our communities with so many benefits, and let’s face it – here in Central Texas possibly the most revered of those benefits is shade. Our large, mature trees provide us with deep shade that keeps our waterways, homes, yards, sidewalks, and even our parked cars cooler. As summertime temps head into the triple digits, TreeFolks would like to remind everyone of some basic information on watering our largest, most valuable trees.
Mature trees benefit greatly from mulch, and really, mulching is the first step to “watering” your trees. Mulch keeps the soil around your trees cooler, shaded, and minimizes evaporation. Large trees’ roots can typically be found within the top 12 inches of soil, and often the feeder roots (the ones absorbing the most water) are found beneath the dripline of the tree, or even further out away from the tree’s trunk. For this reason it is best to set up your watering system near the dripline of the tree, and not any closer to the tree trunk. Watering a tree heavily near its trunk can eventually cause rot and even death.
As with watering young trees, large trees benefit the most from a slow, steady application of water. Since a mature tree will have a widespread root system, it is best to use a drip hose, or at least a sprinkler, to reach the greatest soil surface area. The best time to water trees (and any other plant) is in the morning or evening. It’s difficult to prescribe an application rate, as your tree’s needs will vary based upon its surroundings, but try this:
Water your tree for 2-3 hours using a drip hose or sprinkler. Then take a trowel and gently dig down a few inches into the soil, making sure the water has seeped at least 3 inches down (into the SOIL, not just the mulch). If the soil 3 inches down isn’t wet, turn the water back on and test the water depth again – in a new spot – in an hour. However long it takes you to get the top 3 inches of soil wet, is how long you should water your large trees weekly during the summer. Follow this method unless we receive a substantial amount of rain in a given week.
TreeFolks thanks you for supporting the urban forest by caring for your trees through the summer! Please email education@treefolks.org for more information.
During periods of drought, we recommend watering your mature trees once a week, at least 15-20 gallons at a time. If there’s turf or landscape plants beneath your tree, you may need to apply more water since the tree’s roots are competing for water. Removing the turf within the dripline of the tree and applying mulch in this area will help your tree greatly, but please take care not to damage the roots growing just beneath the soil surface!
Water Appropriately!*
Since most of a tree’s active roots are within the top 12 inches of soil, a good way to water is to put a sprinkler beneath the tree. Place a coffee or soup can close by and run the sprinkler slowly until 2 inches of water has collected in the can. Be sure to water the entire root zone beneath the tree canopy. The best time to water is typically in the morning.
Slow, deep watering every four to six days during drought for mature trees in areas with 95- to 105-degree temperatures (Fahrenheit). In hotter regions, reduce watering frequency as temperatures cool to 75 to 85 degrees. When watering, remember that a tree’s root zone may extend well beyond the tree canopy if there is ample space available.
If turf is underneath the canopy of the tree (whether young or mature), more water will be needed because the turf will absorb much of the water that is applied to the surface. The goal is to get the water through the turf roots and down to the tree roots. Removing the turf around the base of the tree and replacing it with mulch can help eliminate competition for water between the turf and the tree.
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