Leaves on trees planted on the Capitol Square terrace have been yellowing and dropping.
Those visiting the Capitol Square lately might have done a double take. Tree leaves are changing color and dropping, but fall hasn’t arrived just yet. It’s a disorder.
The appearance of trees on the terrace around the Capitol is increasingly strange. “The leaves are yellowing, except the veins are remaining green,” notes Steve Michels, communications director for the state’s Department of Administration.
These are signs of chlorosis, a disorder that can strike a variety of plants. The most obvious symptom is an inability to create chlorophyll. Chlorosis has many potential causes, including damaged roots and a deficiency of minerals including iron, manganese or zinc.
“The grounds crew has taken steps to deal with the chlorosis,” says Michels. The Capitol Square trees have been receiving special treatment since last fall, after the state consulted R. Bruce Allison of the UW-Madison Department of Forest and Wildlife Ecology.
On the advice of Allison, the trees were inspected for girdling roots — roots too-tightly wrapped around the trunk. Trees that showed symptoms have been removed.
“In the fall of 2015 and the spring of 2016 each tree was flushed using a 1 1/2-inch fire hose connected to city hydrants and flushing for three minutes,” to remove any accumulated salts, says Michels.
“The concern is about salt from sidewalks and roads,” explains Brian Hudelson, director of the UW-Madison Plant Disease Diagnostics Clinic.
This spring the grounds crew applied iron and manganese to the soil, to promote root growth and chlorophyll production. Variations in soil quality can complicate treatment of chlorosis, and may require significant ongoing work.
But Michels is optimistic: “We are being proactive and diligent to care for the trees and believe they will recover.”
On Tuesday evening, a tree on the Capitol Square lawn, near Carroll Street and West Washington Avenue, fell on two pedestrians, who were taken to the hospital. The tree had been actively monitored, according to DOA, and showed no signs of stress. The department says other trees will be re-examined.