The National Oceanic and Atmospheric Administration (NAOO) released their prediction for winter precipitation. The bad news? The Great Plains region will continue to experience drought through at least January 2025. This is not good news for Nebraska landscapes, since the entire state is currently experiencing anywhere from abnormally dry to extreme drought conditions.
For a short time, spring rains in 2024 brought most of the state out of the drought conditions we had been experiencing throughout 2022-2033. However, the rain stopped for eastern and central portions of the state in mid-June and drought conditions have been redeveloping ever since.
Tree Response to Drought
Despite spring rain, trees and other woody plants had not yet fully recovered from the 2022-2023 drought. During severe drought, trees are damaged in many ways.
- Reduction in photosynthesis and, consequently, production of energy for growth, defense and storage.
- Reduction in stored energy reserves.
- Death of mycorrhizal fungi. This symbiotic tree root-fungal root association greatly expands a tree’s root system and the tree’s ability to take in nutrients and water from the soil.
- Death of tree root hairs and eventually progressively larger roots.
- Leaf loss.
- Loss of functional xylem, the water moving conductive tissues within a tree’s roots, trunk and branches.
To fully recover, trees must regrow xylem, roots, mycorrhizal fungi and replace stored energy reserves to fully recover. For this reason, woody plants often experience a 2-5 year period of biological lag time in their recovery from drought.
What does all this mean? Redeveloping summer/fall/winter drought continues to worsen the condition of already drought-stressed plants. Long-term drought stress in a tree can lead to decreasing vigor, branch dieback and eventually death of the tree from wood boring insects or disease.
Trees and shrubs not fully hydrated going into winter are also prone to winter desiccation, a common type of winter injury that occurs when the amount of water lost by plants exceeds the amount picked up by the roots. Symptoms seen in spring include brown foliage on evergreens, particularly arborvitae, boxwood and holly, but sometimes also pine, fir and yew. The extent of the symptoms can vary from brown needle tips on one side of the plant, to one or two brown branches, to an entire dead plant. Injury is found on the outer portion of the branches and is often most severe on the side of the tree facing the wind or a source of radiated heat, such as a south or west-facing brick wall or street.
Preventing Winter Drought Damage
Fall watering is a critical step to preventing winter damage to drought-stressed plants. Since daytime temperatures are cooler now, plan on at least one deep soaking for trees and shrubs per month from now until the ground freezes. Use hoses and sprinklers to eliminate the worry over when to winterize an in-ground irrigation system.
Focus on watering the entire area beneath the tree’s dripline and moistening the soil 12-18 inches deep. Move the sprinklers as needed to cover the entire area under the tree. Use a long-bladed screwdriver or piece of rebar to check the depth of water penetration. Once you've reached dry soil, it will be much harder to push the probe into the ground.
What else can I do to help my tree?
Apply a 3 to 6-foot diameter ring of mulch around the base of your trees and shrubs, using 3-4 inches of an organic material, like coarse wood chips. Make sure the mulch is applied in a flat layer, like a pancake, not piled up like a volcano against the plant's bark. Keep it far enough away that it doesn't touch the tree's trunk.
Research has shown trees grow roots significantly better under wood chip mulch than they do under grass. Giving the tree a small area where it doesn’t have to compete with grass roots for moisture and nutrients can help the tree more quickly regrow roots lost during the drought.
So, get out those hoses!
Images
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Winter precipitation prediction from National Oceanic and Atmospheric Administration. Image from NAOO.
- Nebraska landscapes are currently experiencing anywhere from abnormally dry to extreme drought conditions. Image from the U.S. Drought Monitor.