A deep green autumn is rare in Kentucky. By this time of year, our trees usually look forlorn and bedraggled. Dry summers, high temperatures, insects and diseases all take their toll. Not in 2015, though. Our frequent rainfall and cool temperatures have allowed many trees to maintain lush green leaves and to continue growing. Some trees are still producing new shoot growth.
Leaves are a bit like tissue paper, designed for use for only a short time and then discarded. From the time a leaf is formed, a tree invests a limited amount of resources into maintaining it. Shade, drought, insects and fungi all take their toll, so by August, a lot of trees look pretty sad and pale. This is especially true in the Bluegrass and Nashville Basin, where our karst topography leads to water stress even in modest droughts.
The last three years (2013-2015) have been different. Tree growth has extended well into the fall. Today, the first day of meteorological autumn, sees many trees still growing, and leaves of some trees staying dark green.
2015 is even more exceptional. I have rarely seen trees still growing in September, but some of our bur oaks, even some very old trees, are still producing new flushes of growth.
See what the trees in your neighborhood are doing.
Bur oak leaves in August
Eastern redbud leaves, Cercis canadensis
The Old Schoolhouse Oak in August 2015
September flush of growth in bur oak