25 Aug Keeping trees healthy keeps us healthy, too
by Jan Spann
Have you seen tree service trucks in your neighborhood in the past few months? Chalk it up to the abnormally dry conditions in Central Arkansas for the past several years. Drought doesn’t just kill a tree by thirst. Drought puts a tree under chronic stress, leaving it vulnerable to attacks by diseases and pests that a healthy tree could normally survive.
Arkansas’ drought hit hard in 2011 with the hottest summer on record across most of the state. Rainfall during that winter was below average, and the subsoil never had a chance to recharge with moisture, setting the stage for more stress the following summer. Last winter’s U.S. Drought Monitor Map showed nearly half of the state under moderate or severe drought conditions. The spring and summer showers pushed northwest Arkansas counties out of the severe drought range, but it left Central Arkansas counties thirsty for more moisture.
“The impact of drought is cumulative and can take several years to manifest,” said Tamara Walkingstick, associate director of the Arkansas Forest Resources Center (part of the University of Arkansas System Division of Agriculture). “Trees don’t fully recover from prolonged drought.”
While the summer’s assault of leaf-eating caterpillars challenged homeowners, these critters won’t have an impact on a healthy tree. It’s the insect or disease that is present but doesn’t become a problem until something puts the tree in distress. Once weakened, the pest or disease attacks, which almost always leads to tree death.
Drought also reduces photosynthesis in trees, a process that feeds their energy reserves. To conserve water, trees shed leaves — their photosynthetic engines — and this results in reduced energy reserves. Even though native trees can handle drought, a prolonged water shortage requires several years for the tree to rebuild its reserves and fully leaf out again. As trees leaf out in spring, you may note that some trees may have fewer and smaller leaves.
“This could start a downward spiral if the trees can’t produce enough food to sustain themselves,” Walkingstick said.
Watering old established trees once they show the first sign of wilt and or leaf drop may forestall further injury, but catch-up irrigation seldom is enough to change the course of events that the drought has already set in play. Tree roots radiate in all directions from the tree and extend out from the base in a circle approximately equal to the tree’s height.
Tree experts recommend letting a sprinkler run for several hours to provide 1 to 1.5 inches of water per week. Walkingstick also says you shouldn’t expect much visible results from your efforts this growing season, so give the troubled tree a few seasons to rebound before cutting it down.
Recently planted trees also need extra care during drought conditions. Because the roots are confined to a smaller area than established trees, take extra steps to keep the root ball moist. A generous layer of mulch will help mediate soil moisture and keep the soil cooler. Young trees often suffer from bark scald if the trunk is exposed to the sun during the day. Water movement through the trunk is often reduced during the heat of the day when the leaves give off more moisture than the roots can take up. The best time to plant trees is in the fall or early winter, which gives them time to establish stronger roots before the heat of summer.
You can find tree-watering bags that feature a slow release with an even distribution over several hours. Stripped bark on the southwest side of the trunk indicates a problem, so wrap the trunk in burlap, tin foil or a specially designed tree wrap to guard against this injury.
Diseases and insects can be seen through stripped bark, bark stains or “windowpaned” leaves. Regularly check the leaves, both on the ground and on the tree. Don’t be too concerned with trees shedding leaves early, as this indicates the tree is conserving water by doing so.
In most cases, trees that hold their leaves instead of dropping them are in serious decline or already dead. Dogwoods may still retain their burned leaves when fall arrives, but in most cases, they will leaf out normally next spring. Give your trees a few seasons to recover before deciding to replace them.
For more information about forestry, contact your county extension office, or visit the Arkansas Forest Resources Center at afrc.uamont.edu.
If you need to hire a tree service, a few questions will help your find a reputable one. First, ask if they are bonded and insured, which will cover any mistakes or accidents.
Second, ask if they are familiar with “ANSI Standard A300.” This is a set of industry-approved practices. If that sounds complicated, ask instead if they top trees. A reputable tree care professional will not top trees! Topping trees is a terrible horticultural practice and will cause you headaches (and more expense) in the future. Proper pruning dictates thinning out entire branches.
Third, ask for references. Tree service isn’t cheap, so don’t be afraid to check out their work.
Finally, get everything in a written contract. All reputable firms will do this anyway. Get everything you want done written down. Insist that ANSI Standards are followed and that climbing spikes will not be used unless the entire tree is to be removed.
Do not pay for services beforehand, especially in cash! You may choose to secure a second opinion or bid prior to beginning any work.
The Tree Care Industry Association and International Society of Arboriculture are good places to look for more information on arborists and their services.
Trees and humans have a symbiotic relationship: they provide the oxygen we need to breathe, and we expel carbon dioxide that trees need. Even if you’re not a tree-hugger, it’s imperative to your health to nurture the trees you have and to recognize their place on planet earth.