99.8 percent of California is suffering from some state of drought, and it is taking a toll on our trees.
Indeed, without concerted efforts, our state stands to lose much of its natural and urban forests. Unfortunately, the best thing for our trees – copious amounts of water – is not available. So, we must be creative, use our knowledge of tree biology and do what we can to give our trees the best chance of surviving this drought, and ensure they are in the best shape possible to withstand the next one.
Use whatever water you have efficiently. Try to apply enough water to soak the upper 12 inches of soil, where most of a tree’s roots are located. Water the entire drip zone of the tree, but do not wet the trunk or surrounding soil excessively, as this may encourage bacterial and fungal growth. Do not spray the canopy of your trees with water as a significant portion of the water evaporates and never benefits the tree.
Prioritize Your Plants
When water is scarce, always allot the bulk of it to your trees. For one thing, your trees may take decades to replace, should they perish, while you can replace lawns and herbaceous ornamentals within a few months. The replacement value of trees is also considerably higher than the replacement cost and labor for most common ornamentals. So, if forced to choose between your oak trees and your rose bushes, water your oaks, sycamores and redbuds, but let the rose bushes die.
Lose the Lawn
Prioritizing your trees over your plants extends to the lawn. Not only is the water better allocated to your trees, but the lawn’s water needs are fundamentally different than those of your trees. Most mature trees desire infrequent, deep soakings, while grasses typically prefer frequent, light irrigation.
Frequent irrigation causes trees to develop shallow root systems. This not only causes stability problems, and predisposes the trees to failing in high winds; it prevents the trees from accessing deep water reserves. Many people are already making the switch from lawns to arid-adapted gardens or xeriscaping, which not only use less water, but they are better suited for living alongside your trees than a lawn is.
Mulch for Moisture
Mulch is an important tool for maintaining trees in wet periods; in droughts, it is indispensable. The mulch forms an insulating blanket over the roots, which keeps them from being scorched by the hot dry temperatures. Additionally, the mulch reduces the amount of water that evaporates from the soil, which keeps the soil damper than it would be without the mulch. Do not place the mulch directly against the trunk of the tree. Place a 2-inch-thick layer nearest the trunk, increasing to a 4-inch-thick layer near the drip line.
Try to collect and store as much water as possible, which you can use to water your trees. While it may be difficult to collect enough water to water a large, mature tree, scrounging for water can help you accumulate enough water to keep young trees healthy. Consider collecting gray water from your home or installing a rain cistern. When you use water for unusual tasks – such as filing a child’s swimming pool or changing the water in a freshwater aquarium – try to discard the old water inside the drip line of your young trees.
Use caution when deciding to plant new trees during droughts. It can be done, but young, yet-to-be-established trees require consistent watering to keep the root zone damp. If you decide to plant new trees, be mindful of the fact that the next drought may be right around the corner. Avoid planting trees that – even during wet periods — require supplemental watering, such as redwoods (Sequoiasempervirens) and red maples (Acer rubrum). Magnolias (Magnolia ssp.), cherry trees (Prunus spp.), birches (Betula spp.), gum trees (Eucalyptus spp.) and bald cypresses (Taxodium distichum) also require more moisture than Mother Nature provides to southern California.
See the following resources to find more information on keeping your trees healthy during the drought: