Drought is a meteorological event defined as the absence of sufficient rainfall over a period of time resulting in a depletion of soil moisture.
Most of Oklahoma is currently in a severe to extreme drought condition.
Officially, Oklahoma City is 5” below normal rainfall amounts for the year.
“Normal” can be misleading. Since late May, most of the metro area rainfall has come from a couple heavy rainfall events. And, since the last heavy rainfall event 5 weeks ago, we have been void of any rainfall.
When it comes to your lawn and landscape, the frequency of rainfall is more important than the total amount of rainfall year to date.
Long before the local weathermen started talking about drought conditions in our area, we were seeing the symptoms of drought on lawns and landscapes because the occasional rainfalls of the summer and fall were missing this year.
Without an occasional rainfall every deficiency in an irrigation system is noticeable. In this picture a tree is preventing a strip from receiving the much needed head to head irrigation coverage for seed to germinate.
What You Need to Know… Water is Very Important
Water is the lifeblood of all living organisms.
Without water there is no plant life.
Most often we are overly focused on the visible and not focused enough on the invisible. We worry about leaves and needles turning brown and falling off, while the real concern is the condition of the roots.
The root system of all plants (trees, shrubs, groundcovers, flowers, and lawns) is affected by drought before we see the visible signs of drought.
Water is primarily used by a plant to uptake and transport nutrients. Lack of water limits the plant’s ability to move food and minerals around.
Feeder roots are responsible for water uptake and are primarily located in the top 12-15” of the soil. When the available moisture declines to the point that there isn’t any available for the feeder roots, root damage occurs and if conditions persist feeder roots begin to die back.
Root loss leads to stress and dramatic increase in susceptibility to insects and disease.
Broadleaf evergreen plants are the first to be damaged in a drought. It is common for evergreens to appear to be surviving well until they suddenly die.
Many responses to a drought will not appear until the year following a drought. Spring flowering shrubs and trees may have reduced flowering the following year after a drought.
A drought can start a cycle of decline that a plant may never recover from resulting in plant loss months or even years after the drought.
It can take multiple years of normal precipitation for trees to regain their full health following a drought.
In periods of drought, it is not uncommon for an evergreen to appear healthy and then die suddenly. Often a quick death is the result of a cycle of decline from previous drought periods from which the plant never fully recovered.
Why You Need to Know… The Effects of Drought on Your Lawn and Landscape
The result is less growth, poor color in leaves, leaf drop, and a thinning or dying top.
On smaller, newer trees and shrubs, the impact of a drought is evident with yellowing, wilting and then finally the plant dies.
Newly planted trees and shrubs suffer more during a drought because they already have a reduced root system.
Mature plants with extensive root systems may not show signs of drought stress, but damage is still occurring.
Pest and diseases increase during drought. Plants produce defensive compounds when they are healthy, as they become stressed, they struggle to defend themselves. Borers are common in drought stressed plants.
Throughout the late summer and fall lawns that have not been watered or have poor irrigation coverage have gone prematurely dormant. It’s easy to tell if a lawn is loosing color due to lack of moisture, the cores we pull are powdery dry several inches below the surface.
Signs of Drought Stress
These signs apply primarily to trees, but in some form or another, these signs will be visible in all plants including lawns.
Temporary Wilting. Wilting will occur during the day. Leaves will recover and appear normal in the morning.
Permanent Wilting. As the drought continues leaves remain wilted all the time.
Yellowing Leaves. Leaves turn yellow and can exhibit fall color out of season.
Leaf Scorch. Leaf margins will have a brown or burned appearance.
Defoliating Trees. Tress will lose leaves from the top and ends of branches.
Bark Cracks. During prolonged droughts trees may develop cracks in the bark, especially in thin-barked species.
Dead Branches. The top and outer tips will begin to die.
Thinning Foliage. The canopy will appear sparse.
Small Leaves. New leaves will be unusually small.
Slowed Growth. Growth will slow and nearly stop
Increased Susceptibility to Pests. Borers or fungal disease will develop.
A visual sign of severe drought for a tree is permanent wilting followed by loss of leaves.
Yellowing leaves are a sign of drought stress. By the time a tree reaches this point the feeder roots are under stress and may be to the point of dying.
Another sign of drought stress for a tree is leaf scorch. Leaf margins have a burned appearance. In this picture taken in August the tree is exhibiting fall color out of season.
A Bald Cypress tree that is in the process of defoliating in the late summer due to lack of moisture.
Landscape Winter Hardiness
Few plants planted in the correct USDA hardiness zone die directly from cold weather. Winterkill is commonly a result of an unhealthy plant.
Lack of adequate soil moisture is often a major cause of winter damage.
All plants, especially evergreens, use water during winter.
When you pull a dry core from a lawn in the fall you know there is a chance the lawn may not have the stored nutrients required to overwinter well.
What You Need to Do…Best Practices to Prevent Drought Damage
Fall and winter irrigation is very important, especially with this year’s conditions.
Lawns and landscapes should be watered thoroughly in the fall to prepare them for the winter months.
Through the fall, lawns and landscapes need 1” of water per week. This applies for both fescue and fescue lawns, as well as trees and shrubs. Whenever we receive ½” of rain or more you can delay watering for a few days.
How long do you need to water to get 1” of water? Place a Hall | Stewart Rain Gauge or any small container in your lawn or landscape, run your irrigation through a cycle, and then check the amount of water. If you have ½” of water, you need to water 2 times per week through the fall.
Water deep. If you can get 1” of water on your lawn without excessive runoff in one event, water once per week. Deep watering creates deep roots and a more drought tolerant lawn and landscape.
Adding mulch around trees and shrubs improves the soil’s ability to hold moisture. Apply 2” to 4” of an organic mulch. Pull mulch away from the plant trunk 2”. Our preferred mulch is a grade A, all bark, shredded cedar.
Remember, even mature, healthy trees need supplemental watering to help them through a drought. Focus on watering around the dripline and a little beyond. Roots extend 2 to 3 times the trees dripline. The dripline is the circumference of the tree's canopy, where the water drips onto the ground.
Fall and winter watering is especially important for trees and shrubs planted in the last 2 years. Until the roots grow into the surrounding soil the plant has limited roots for supplying moisture.
During the winter, your lawn and landscape requires 1” of water every two weeks. Whenever we go a week without any rain or snowfall, pick a nice day and give the landscape a good soaking.
You can test soil moisture with a long screwdriver. If the screwdriver goes into the soil easily, watering may not be needed. If getting the screwdriver into the soil is difficult, your landscape needs water.
A gator bag is a great tool for slow and deep watering a tree.
At Hall | Stewart our goal is to help you have your best lawn and landscape and provide you with the information you need.
The lack of rainfall this summer and fall has become a major concern for our customers. We hope you did not give up on watering your lawn and landscape too early this fall.
If you did, please resume best watering practices. Your investment in your lawn and landscape is significant.
If you have questions about the impact of drought on your lawn and landscape, please call or respond to this email. We would love to hear from you.
Lorne Hall
Hall | Stewart
(405)367-3873