Hand-watering with a hose is still the most precise method for watering trees.
Watering new treesA newly planted tree requires more care since it doesn’t have a root system large enough to obtain sufficient water. To maintain healthy root ball moisture, apply 1 gallon of water per diameter inch of the tree trunk per watering event. Use a hose, drip, bucket or tree watering bag for best results. Follow a prescription of frequent, consistent and light irrigations to establish a tree — aka the 3-2-1 watering method:
After six months, water two to four times a month.
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When your supplemental irrigation is limited to specific watering hours during drought, trees are always a wise place to focus your watering efforts.
Although the size of mature trees demonstrates they’ve survived drought on their own many times before, experts suggest providing additional water if they’ve received no supplemental water or rainfall for more than four weeks. Thankfully, recent rains in San Antonio were a shot-in-the-arm at just the right time.
Trees, of course, are accustomed to our weather patterns in South Central Texas and they typically receive most of their warm-season moisture, if any, in late spring and late summer. But in the event that July and August provide no beneficial rainfall, it’s always helpful to review when to water and where to apply it.
You can fit supplemental tree watering within existing watering windows. Hand-watering with a hose is still the most precise method for watering trees. A water wand with a cut-off adds a touch of ergonomic elegance.
Apply in a circular motion to allow water to soak in thoroughly. An inch of water can percolate 6 inches into the soil where many of a tree’s water-absorbing tree roots are located.
For trees, water absorption is handled not by thick woody roots but by the fine, hairlike feeder roots (the kind your shovel cuts through like butter when you’re digging a hole). Although they may seem delicate, they play a vital role in absorbing nutrients and water for the entire tree. And in ideal circumstances, they may grow outward twice the width of the canopy height. They tend to occur in the highest density where water funnels every time it rains.
Once you understand this concept, you can use it to your advantage when applying water:
- Around the tree trunk’s root ball (at least 10 inches away from the trunk).
- Along the drip line. Think of an umbrella: the drip line is the circle around the perimeter where water sheds directly from the canopy to the ground.
During drought, when your goal is not really growing the tree larger but helping it survive, the area around the trunk well inside the drip line is a good area to focus on. In part because the density of roots may be higher a little closer to the trunk and also because the tree’s shade keeps water from immediately evaporating, allowing it to be absorbed.
As usual, avoid wetting the trunk itself — start at least 10 inches away from the bark — and avoid obsessively oversaturating the soil under your trees. Remember, fine roots grow close to the surface not just for water but also for oxygen. Too much water can suffocate them!
Watering trees once-a-month during drought can seem time consuming, but it’s just a part of keeping them healthy. Avoid adding additional stress, especially during drought.
- Don’t prune excessively. Instead, use a certified arborist for major pruning (generally on a five-year cycle) and listen to their suggestions.
- Don’t install new sod or artificial turf during a drought; it can interrupt the function and recovery of a tree’s fine root system. Instead, add mulch (less than 2 inches) or compost (1/2 inch per year) to increase your soil’s moisture-holding capacity.
- Don’t use high-nitrogen fertilizer or weed-and-feed products around trees as they can cause rapid growth and quickly use up a tree’s energy stores.
- Don’t disturb the area under a tree’s canopy. Digging, trenching and compacting the ground around a tree will impact the fine feeder roots that provide water and nutrition.
Remember, maintaining a healthy shade canopy is never a “set it and forget it” process. As trees grow, they may tend to become overcrowded and begin to thin themselves out on their own.
Each winter (October through February) is a chance to have a licensed arborist conduct any pruning and, if necessary, diversify your existing tree selection by planting new ones so they can get established before hot weather arrives.
WaterSaver landscape beds are a great place to start new trees since they’re safe from the lawnmower and they’re already mulched!
CPS Energy Green Shade Tree Rebate provides a list of trees that may be appropriate for your site. For more on individual species, use the Find a Plant feature and to learn more about watering and caring for trees, visit GardenStyleSA.com.
