Feature Story
OVERHEAD AND (Sometimes) OVERLOOKED: Knoxville’s Urban Forester Explores and Explains 10 Years of Change to the City’s Tree Canopy
By Kasey Krouse, City of Knoxville Urban Forester, with Bill Klingeman, UT Plant Sciences Department
In
Fig. 1. Insect-vectored bacterial leaf scorch caused extensive decline in tree crowns, requiring removal of sycamore trees (Platanus occidentalis) that had been planted along the 3rd Creek Greenway Trail (Top). (Inset) Leaf scorch symptoms caused by Xylella fastidiosa are apparent as necrosis on leaf margins (Photos by Kasey Krouse). 14
tennessee greentimes SUMMER 2020
2011, trees surveyed for an Urban Forest Management Plan documented that the Top 4 genera of trees within the City of Knoxville’s managed landscape consisted of maples (21%, Acer spp.), oaks (14%, Quercus spp.), dogwood (11%, Cornus spp.), and sycamore (6%, Platanus spp.), with the remaining 47% of trees spread among other genera. Yet the most abundant tree species within our landscapes are not always the most successful, either with establishment or maintaining tree health across time. Flash forward to 2019 and these genera still comprise the Top 4, yet their prominence as Knoxville tree canopy components has shifted: now to maples (19%), oaks (13%), dogwood (8%), and sycamore (4%). The story of these trees, and of the other 55% of Knoxville’s increasingly diverse tree canopy, is the focus of this article. At about the same time that the 2011 Urban Forest Inventory was concluded, Knoxville and East Tennessee faced threats from Emerald ash borer (Agrilus planipennis) to ash trees, bacterial leaf scorch (Xylella fastidiosa) to sycamore trees and pin oak (Fig. 1),
