Summer 2022 is shaping up to see a return to drought conditions with little rain and temperatures already hotter than we have seen in a decade. We already have customers asking about how best to water trees for maximum benefit. Here’s our recommendations for here in Central Texas:
Trees require a slow watering and deep soaking, basically mimicking rainfall. For the average homeowner, this simply means watering your trees from the trunk to the dripline (Called the Critical Root Zone, or CRZ) with a garden hose once every 1-2 weeks in the summer and monthly in dry winter months.
If temperatures are extremely hot, hovering around or over 100 degrees, and you’ve had no rain for several weeks, you may want to water the CRZ weekly. In a typical Austin summer, watering every two weeks is fine if temperatures are tolerable and we’ve had summer rain. Keep in mind this area often has late spring and summer water restrictions, so you should be aware of and adhere to them. Most water restrictions do not apply to hand watering in Austin and surrounding cities, but check with your local municipality for local watering rules because you can get fined.
You can water your trees using a garden hose, a lawn “doughnut” type sprinkler, or a soaker hose. If you are going to use a sprinkler or soaker hose, we recommend using a timer to make sure you do not leave the water running for an extended time. Water is expensive during droughts periods. Leaving the water running for several hours, or worse, overnight can cost you not just with a higher water bill but maybe a fine for excessive use. I have had many customers tell me that they have left their water running, forgetting to turn it off, resulting in outrageous summer water bills. That said, remember ANY water you give your trees during drought conditions is better than nothing.
Trees typically need 5-10 gallons of water per inch of trunk diameter on the HIGH end. Keep in mind this is diameter through the center of the trunk, and NOT circumference which is a much higher number. Most medium to large Austin area live oaks are 15-25 inches in diameter, which means no more than 45-125 gallons of water per tree. In Central Texas, most absorbing tree roots are within the surface soil, at 6-8 inches below the surface OR LESS! Once the water goes below these absorbing roots, it goes to groundwater, but the water DOES have to pass the absorbing roots in order for the tree to get access. This means that you have to soak this surface area for a period of time in order to allow the tree access to the water. The term “deep watering” is actually nonsense, because the absorbing roots and the associated symbiotic fungal mycorrhizae that take up a tree’s water typically do not exist lower than 8-10 inches even in the deepest of soil (unless there is a cave below the surface). On slopes, or when watering trees growing in heavily compacted soils, slower watering is required to prevent runoff.
If you want to know if you have watered enough, dig down into the soil with a trowel 24 hours after watering, or use a screwdriver. If the soil is moist to a depth of 5 inches below the surface, you have watered adequately. You can also buy little gadgets called soil water meters. You can poke these devices into the soil, and they will tell you how much moisture it has (you can find them on Amazon).
Tree Watering Chart
| DIAMETER (TREE SIZE) IN INCHES | GALLONS OF WATER NEEDED |
| 0-5 | 1-5 |
| 6-10 | 10-20 |
| 11-15 | 30-45 |
| 16-20 | 60-80 |
| 21-25 | 100-125 |
| 26-30 | 150-180 |
Mulching over as much of the critical root zone as possible will help reduce evaporation between water events, and help maintain soil health over time. Additionally, well fertilized trees are more vigorous and better able to withstand drought conditions.
Regardless of any of these tips, the biggest tip I can give is this: DO NOT apply herbicides or weed and feed type products within or to the critical root zones. These products will not only damage the trees, but can actually kill some species such as post oaks, and they are MUCH worse during drought conditions, where trees take up liquids much faster and they have less water in their systems to dilute the chemicals.
Please contact us if you need an arborist to assess your trees. We do provide extremely effective fertilization programs designed for maximum effectiveness under the extreme weather conditions we experience here. As always, we are here to help!
