Help your trees survive the drought
The drought of 2012 has taken a toll on plants across the country, devastating corn and soy bean crops, wreaking havoc on landscaping and ruining lawns.
While you might be worried about your grass turning brown or flowers wilting, there’s one thing that you definitely shouldn’t overlook - your trees.
Like all plants, trees require a consistent supply of water, but when they’re under prolonged exposure to drought conditions, they can suffer irreversible damage. A professional tree service can assess the health of your trees and look for drought-related stress. Many tree service companies employ a certified arborist, which is a professional who specializes in the cultivation and management of trees and other woody plants.
Signs of stress
“Drought stress on mature trees includes wilting or yellow foliage, brown scorched areas on leaves, premature leaf drop, limb dieback and overall thinning of the canopy,” says Paul Goin, a certified arborist and owner of highly rated Tree Pros in Denver. “Conifers will show signs of drought by the needles, browning from the outside inward.”
Wesley Kocher of the International Society of Arboriculture says the most obvious sign of drought stress is defoliation - when trees shed their leaves. “The tree takes water up through its roots and brings it to the leaf, and then the leaf evaporates water off into the air,” he says. “If the tree doesn’t have the energy to sustain the leaf anymore, it will drop the leaf. It’s like a coping mechanism for the tree.”
Jud Scott, a certified arborist and president of highly rated tree service Vine & Branch in Carmel, Ind., says the drought is affecting all types of trees, but young trees have it the worst. “New trees have less roots established and are hit harder by drought,” he says. He warns that mature trees near driveways and house foundations, or in areas with utility lines might also be at a higher risk due to root loss.
“Mature trees have been able to develop more extensive root systems, and therefore are able to obtain water from sources underground,” Goin says. “Newly planted or young trees require more attention during drought.”
Kocher says trees are at the greatest risk of dying during the first two to three years after being transplanted to the ground. “That’s when you really want to pay attention to the watering and to the stresses of the tree," he says.
Water conservation should be exercised during a drought, so watering directly with a hose or 5-gallon bucket rather than a sprinkler will help ensure the water is going to the tree and not your sidewalk or driveway. You should focus watering on the drip line, which is the area on the ground directly under the tree canopy where feeder roots collect moisture.
“You want to make sure the water is reaching the tree roots and you’re doing a deep soak, not just lightly watering the top of the soil,” Kocher says. “Make sure it’s soaked through the first foot of soil, that’s where a majority of tree roots are.”
Arborists recommend watering young trees twice per week and mature trees once per week. Mature trees require the equivalent of 1 to 1.5 inches of rain per week during the growing season.
There are a few techniques to determine how much water to use. Some arborists say you should add 10 gallons of water for every inch of tree diameter. Another method is to apply between 1/2 and 2/3 of a gallon of water for every square foot of soil under the drip line. Ideally, a tree with a 20-foot drip line should get about 150 gallons of water per week, but due to drought conditions or high utility costs, it's not always feasible. To put it in perspective, a typical bathtub holds about 50 gallons of water, so it would be like filling up a bathtub three times over.
Watering early in the morning or after the sun is set will reduce evaporation and help the water to soak into the soil. If you do use a sprinkler, make sure you're not wasting water by spraying outside of the tree’s drip line. To measure how much you’re watering, place an empty tuna can or similar container inside the spray area. When it’s full, you’ve watered enough.
Adding a layer of mulch around the base of a tree will help it retain moisture. However, you should avoid piling mulch higher than 4 inches because it can create excessive moisture, which can block oxygen to the roots or cause root rot.
For more information, visit the Angie’s List Guide to Tree Services.