By Brandy VanDeWalle, UNL Fillmore County Extension Educator
Every year, there seems to be an issue with trees, whether it is a disease, insect or simply an environmental cause. This year was no exception and an article recently published by Kelly Feehan who is a horticulture extension educator in Platte County addressed common concerns with trees and great strategies for replacing trees. Below is Kelly’s column:
This summer appeared to be hard on trees as we saw an increase in branch and tree death. It was not our summer that caused stress but a culmination of weather extremes over past years. Abnormal weather leads to environmental stress because trees are best adapted to gradual changes. Sudden changes in temperature can cause direct injury to trees or set them up for attack by diseases and insects.
Weather extremes have always been the norm for Nebraska. However, due to climate variability, weather extremes are predicated to become even more extreme. Since trees provide environmental benefits and increase community and property value, how do we guard against tree issues and tree death? We start by planting for diversity, selecting quality trees, planting correctly, and following good tree care practices.
When diagnosing tree problems, it’s not unusual for me to tell a property owner had they NOT done this or that, the tree might not be having an issue. They usually respond, “If I’d only known.”
Here are tree practices to AVOID improving tree health and longevity. I have talked about these in previous columns, but they bear repeating with fall planting season here. To begin with, we need to stop overplanting singletree species, stop planting overly large trees, stop planting too deep, stop overwatering, stop over fertilizing with nitrogen, and stop mulching too heavily. Notice most of these are examples of over doing it. The tendency to overdo shows how much we value trees and want them to do well. But too much of a good thing is rarely a good thing for trees.
I am often asked what tree is best to plant. With weather extremes increasing, this is somewhat of an unknown so plant for diversity. If three trees are to be planted, plant three different trees. If three windbreak rows are being planted, use at least three different trees if not six or more. Some trees have known issues. Ask about potential issues before selecting a tree. If planting a tree this fall, e-mail me for a list of recommended trees. Trees to avoid are also on the list. Her e-mail is firstname.lastname@example.org.
On the recommendation to stop planting overly large trees, what is a good size? The smaller the better from the trees standpoint (if rabbits and lawn mowers are kept away); but most of us prefer to not start with a seedling. Do be aware research shows smaller trees catch up and surpass larger trees and often have fewer issues such as girdling roots and less transplant shock. Start with the smallest tree you are comfortable with.
Avoid planting too deep by locating the trunk taper BEFORE digging the hole. Do not plant the tree at the same depth it is in the container. More often than not, trees are planted too deep in the containers. And cut any circling roots that can be seen. Dig planting holes to the depth that allows the root ball to be placed on solid ground, leaving the trunk taper above ground. Be sure to dig the hole wider than the root ball to loosen surrounding soil. Roots grow outward, not downward. Keep the soil good and moist, especially for the first week or two. Then keep the soil moist but avoid a saturated soil or a planting hole that is full of water. Use a two to four inch layer of mulch in at least a four-foot diameter ring. Avoid too deep of mulch or mulch piled against the trunk.
Do not fertilize at planting with nitrogen. This will increase transplant shock. And if the tree is planted in a fertilized lawn, do not add additional nitrogen to the tree. This is a waste of money; and excess nitrogen sets trees up for increased environmental stress and attack by diseases and insects.