After one of the warmest Nebraska winters since the Dust Bowl and a drought across much of Nebraska, state forestry officials are urging homeowners to pay close attention to their trees.
Brad Kindler, a sustainable landscape specialist with the Nebraska Forest Service, said trees that have been recently planted are at the greatest risk of drought stress.
“A tree that's been planted within the last one to three years needs supplemental water as a way to get that root system tapped into the existing soil structure,” Kindler said. “A tree that's been in the ground for many years or decades already has that established period.”
Kindler said identifying drought stress can look different depending on whether a tree is an evergreen or deciduous species.
Evergreens, which continue to photosynthesize and respirate throughout the winter, are more susceptible to winter drought. They should be watered as early as possible in the spring.
Deciduous trees can be trickier to read. Because they go dormant in the winter, drought damage may not be visible until later in the growing season. Homeowners should watch for wilting, dropping or yellowing leaves.
Mike Comstock, Lincoln parks operations coordinator, said property owners should wait until later in the spring when trees begin budding and leafing out to assess damage.
“If there’s any concern on larger trees, they probably should have it inspected by a certified arborist, just to make sure there's not any kind of hazard,” Comstock said, especially for trees near homes.
Kindler said getting water to a stressed tree is always worth trying, even when it has already been attacked by pests or disease.
“The act of watering really gives it the opportunity to hopefully overcome whatever issues might be associated with other types of opportunistic infections,” Kindler said.
He said a tree has likely passed the point of saving when disease or pests have compromised its structural integrity or its ability to move water and nutrients through its canopy. Kindler said treatment may still be an option depending on the tree’s value, if it holds historical or family significance.
The Nebraska Forest Service recommends five gallons of water per week during the establishment period, which can last a couple of years. If the tree receives at least an inch of rainfall per week, the amount of water can be reduced.
Water should be applied around the drip line, the edge of the tree’s canopy, at the base of the tree. Kindler recommends placing mulch around the base of the tree to reduce soil evaporation and protect the tree from lawn equipment.
Native and locally adapted species are best for drought-prone areas. Once established, these trees are better equipped to handle dry conditions.
Kindler said the bur oak, native to Nebraska, has an expectational ability to weather drought across the entire state. Hackberries, ponderosa pine and limber pine, especially in western Nebraska, are all drought-tolerant.
But deepening drought over the last six years has killed a range of native Nebraska trees in eastern Nebraska, including the state’s oldest at Ponca State Park. It’s put a stress on state and city forestry crews who are rapidly working to replace Nebraska’s aging and dying tree canopy.
Each year the City of Lincoln plants around 500 to 600 trees in parks through volunteer events each spring and fall. The city also offers a street tree voucher program, which provides $300 in cost share assistance to residents who want to plant a tree in the right-of-way space between the sidewalk and the street.
Homeowners are responsible for the initial watering period, but the city takes over long-term maintenance, including trimming and removal. Residents can apply through the city of Lincoln's website.
Hypoxylon canker, a fungal disease that affected bur oak trees at Mahoney State Park and other areas around the state, takes hold when trees are already weakened by stress such as drought, heat or soil compaction.
Kindler said the forest service has not seen any large-scale instances of the disease elsewhere in the state, but emphasized that reducing stress factors, proper watering and monitoring for pests, is the best defense.
Despite the challenges from drought and pests, Kindler said he hopes Nebraskans keep planting.
“The best time to plant a tree is 10 years ago,” Kindler said. “Even in the context of drought, our hope is that people are out there planting trees and managing the landscapes they have, because the benefits of these trees are important to us statewide.”