As a horticulture extension agent, my job mostly entails answering questions of a plant related nature. This could be anything from identification of weeds, insect identification, or solutions to a disease in the landscape. I try to keep a record of all the questions that I get so that I can help homeowners steer clear of some of those problem plants that are having issues. These are my top trees to steer clear of this 2020.
Leyland Cypress (xCupressocyparis leylandii) will always be at the top of my list and I continue to get questions about this evergreen even during the wintertime. We see this tree planted in screens in order to add a privacy boundary around the lawn. This tree is plagued with issues and it will only continue to have issues in Tennessee. It is not drought tolerant, not tolerant of poorly drained sites, and seems to be prone to bagworms and Seridium Canker. Seridium Canker is a fungus and large sections of the tree will turn brown and die. It's easy to spot because there will be sap oozing from the infected branches. When one tree in a screen becomes infected with a disease, the disease will slowly go down the entire row.
Bradford Pear (Pyrus calleryana "Bradford") is a tree that was touted as the perfect tree for the home and we see many lining driveways throughout our county. Every Bradford Pear has an expiration date on it because they seem to have such weak stem growth that they are prone to splitting. Another issue with this tree are the invasive characteristics of it. We see white blooming shrubby trees all along the interstate and these are all Bradford Pear seedlings that are now plaguing our abandoned fields and open landscapes.
Pin Oak (Quercus palustris) is one of the largest shade trees that one can plant in the landscape. Typically, oaks don't have any issues in the home landscape, but one issue has surfaced in the recent years that cannot be treated. It is called Bacterial Leaf Scorch. This bacterium gets inside the tree and affects the xylem, which is the water-transporting vessel of the tree. It is called bacterial leaf scorch because the edges will get a scorched look to them, mimicking drought stress. This usually occurs in the middle of summer and most homeowners will think it is drought stress. One other sign of bacterial leaf scorch is the bottom branches will lose all of their leaves in midsummer. Unfortunately, there is no treatment for this disease and the tree will succumb to the bacterium within a few years. Pin oaks seem to be the oak species that I've seen with it most because they are one of the most widely planted landscape trees today.
As always, if you have any questions regarding any horticulture facet, feel free to contact Lucas Holman, Horticulture UT-TSU Extension Agent, Wilson County at 615-444-9584 or Lholman1@utk.edu.