(Backyard Gardener - Photo Illustration - MetroCreativeConnection)

Hello Mid-Ohio Valley gardeners and farmers! Dry conditions continue as we get a short, yet sweet taste of cool fall weather. After a record low temperature of 46 degrees F Wednesday night, we are looking at seven days in a row of 90 degree heat.

Since 1900, West Virginia has experienced several noteworthy droughts, including 1904, 1930-31, 1941, 1954, 1966, and 1988. During the drought of 1930-31, nearly 100% of the Mountain State experienced what currently would be referred to as D4, or “exceptional drought,” for eight months.

More than 60% of West Virginia is currently in a drought, with at least part of every county experiencing abnormally dry conditions. More information can be found at the U.S. Drought Monitor website at drought.gov.

This week I want to discuss the effects of dry weather and drought on trees and landscape plants. We obviously see the effects of lack of rain on our lawns. Many people are only mowing once every four weeks when typically we will mow at least once a week with adequate rainfall. Many lawns have turned brown and grass growth has slowed significantly.

However, as I travel through the Valley, I see lots of Johnson grass thriving in hayfields and along roadsides. It is a warm season grass, so it will grow in hot, dry weather compared to our cool season grasses. Keep in mind that the ideal temperature range for warm season grasses is 80-95 degrees Fahrenheit.

Backyard gardeners need to be concerned with any newly planted trees and shrubs. Most homeowners realize newly planted landscape trees need to be watered in order to establish roots, but often the amount and frequency of water needed is underestimated.

Water is essential to plant life. Water serves as the raw material for many metabolic processes, including photosynthesis. It plays a significant role in the elongation of newly formed cells and the growth of woody plants.

The uptake and transport of mineral nutrients also occurs in water. Minerals dissolved in soil water move into plant roots and then to the vascular system, (called the xylem) for transport throughout the plant. There they combine with proteins to form enzymes that control the biochemical reactions essential to plant health and growth.

The effect of drought is particularly acute for newly transplanted trees and shrubs since they are already devoid of a sizable portion of their water-absorbing roots (feeder roots). These roots are lost in the digging and transplanting process.

Consider how a tree or shrub is dug up and transplanted. The tree has been nurtured in a nursery for years and watered every day. Suddenly, it’s transplanted, destroying most of the “feeder roots,” the tiny root hairs efficient at absorbing water and nutrients.

In the root system of a tree or shrub, the delicate root hairs that extend from epidermal cells and feeder roots at the extremities of the root system are responsible for the bulk of water uptake.

Confined to the upper 15 inches or so of the soil profile, they are also the first part of the root system affected by dry soil conditions. The water absorbing capacity of the plant is severely reduced by the death of root hairs.

What are some of the symptoms of drought stress? Drought symptoms include browning across the entire tree, but trees with damage to the root system will have large areas of dying foliage on the side of the crown. Immediate visible effects include wilting, scorch, and early leaf loss (defoliation). During prolonged droughts, trees might develop longitudinal cracks in the bark, especially in thin-barked species like maples.

Leaf scorch occurs when leaves turn yellow-brown starting from the outside edges. Leaves can also become chlorotic with a yellow or yellow-green color. In the event of damage to the root system, trees often lose their canopy (defoliation), starting at the top and middle of the crown.

On evergreens (conifers), brown needles and wilted, drooping growth (twigs) are usual signs of prolonged moisture stress. As a drought extends over several months, dieback in the upper crown of the tree may also be noticeable or sucker-twig growth along the trunk on some species may occur.

Drought stressed trees are more susceptible to diseases, pests, and structural damage than they would be under normal conditions. Lack of water reduces a tree’s ability to absorb and transport minerals or nutrients.

Metabolic processes such as photosynthesis may decrease or cease entirely if drought conditions become very severe. During a drought, fine root hairs die, reducing capacity to absorb water. Drought effects can vary, depending on tree species, health, vigor, and location.

The effects of drought may not become evident for several years until weakened branches break in storms. Decline (called tree dieback) can continue for the next few years as trees use up their energy reserves to recover water and nutrients needed for long term growth. As drought persists, branch dieback continues in the same pattern, starting at the middle top and spreading into the interior of the crown.

Many trees may take three years to die, and some will hang on until five years after the drought. As these trees decline, they are more susceptible to insect and disease infestations.

Water requirements for trees are substantial, particularly for large trees. For example, a large tree can lose water at a rate of over 100 gallons per day. An inch of rainfall equates to over 27,000 gallons (113 tons) of water per acre.

Over 90% of this water is lost through the process of transpiration. Evaporation of water from the leaves allows water molecules to move from the absorbing roots through the trunk and into the branches. Lack of water means essential nutrients needed for growth are unable to be transported and complete their photosynthetic processes.

Replacing this level of water can be difficult, costly, and unsustainable from a water resource perspective. The good news is that it is often unnecessary for most mature and well-established trees.

Established and healthy trees have an expansive root system capable of supplying some of this water. As a result, only supplemental watering is needed to help trees through periodic droughts. The following is a guideline to help with watering established trees (Alabama Extension).

Soil should be moist to a depth of 12 inches below the surface. Slow, deep watering is preferred over fast, shallow watering. Water for a long time to saturate the soil to a great depth and encourage deep root growth for better adaptation to the site. Newly planted trees need at least 1 inch of rain per week, but they do not have enough water-absorbing roots when freshly planted.

A few words of wisdom on planting trees. Plant tree species suited to your site. In other words, do not plant a water-loving tree in a dry location. Consider using plants adapted to dry climates in landscaping.

Do not fertilize trees that are water-stressed. Artificial fertilizers are made of salt and can make conditions worse. Nitrogen encourages growth, which only serves to increase demand for water. Do not prune a drought-stressed tree except to reduce risk of branch failure.

Trees on a slope or on sandy soils may need more watering than trees in soils that hold more water. Trees on a slope may also need a soaker hose or drip emitter. Never transplant a tree during a drought. It most likely will not survive because it can’t establish its root system.

Water the tree’s entire growing area. Roots extend two to three times the tree’s dripline. So watering the entire root system is difficult. Instead, focus on watering the entire area under the tree’s dripline and a bit beyond, if possible. Covering more area is better. Avoid watering the tree’s trunk or foliage. This can promote disease and insect outbreaks.

Water deeply. It is important to ensure water penetrates deep into the soil so water deeply. For mature trees, deep periodic watering is preferable to frequent shallow irrigation. Frequent shallow irrigation promotes shallow rooting and increasingly less drought-tolerant trees.

If rain does not occur for a three-week period, consider watering trees and shrubs once a week until rains resume. A heavy complete watering is more effective than shallow watering. Shallow watering will encourage shallow rooting which can lead to root damage during a severe drought.

Trees are readily adaptable to water stress, but long-term drought conditions can lead to decreased overall tree health and increased likelihood of tree death. Signs of prolonged drought stress include leaf scorch, dieback, and root problems. Homeowners can lessen effects of drought by planting the right tree in the right place and using slow, systematic irrigation and mulch.

Contact me with questions at the Wood County WVU Extension Office at 304-424-1960 or at jj.barrett@mail.wvu.edu. Until next time, Good Luck and Happy Gardening!