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August 2026: Pin Oak
by Andy Mead
Our Tree of the Month for August is a pin oak (Quercus palustris) on Kilrush Drive
in Cardinal Valley. We’re featuring it to encourage people to not plant this species and to understand why this once wildly planted and appreciated tree is not a wise choice. The tree appears to be healthy but could be showing signs of leaf scorch. In many cases, Lexington has had bad experiences with pin oaks.
If you have a pin oak that appears to be healthy, Trees Lexington is not encouraging you to remove it. The tree has benefits that are listed below, but may need more care at some point.
For much of the last century, pin oaks were Lexington’s go-to tree. They were planted in parks and yards and lined the driveways of horse farms. They grew fast and, with pruning of downward-pointing lower limbs, had tall, straight trunks that seemed to make them the perfect street tree. They offered nesting and cover to birds and mammals. Their acorns are bitter but feed a lot of wildlife after white oak acorns are gone. More than 40 species of caterpillars fed on their leaves. Dave Leonard, a long-time Lexington arborist and a member of the Trees Lexington board, recalls a survey in the late 1980s estimated that 90 percent of the city’s tree cover was pin oaks.
But pin oak leaves started turning brown and soon trees were dying. The culprit was – and is -- bacterial leaf scorch (BLS), caused by an insect-spread bacterium called Xylella fastifdiosa. The disease makes the trees die of thirst, even in the wettest years, by clogging the tissues that carry water through the tree. There is no cure for BLS, but treatments are available to suppress symptoms and prolong the tree’s life. The bacteria has been identified in other plants around the world. It most notably has attacked red oaks (Quercus ruba).
By the end of the century, chainsaws were felling them all over town. And large oak trees are expensive to remove.
But bacterial leaf scorch isn’t the pin oak’s only problem. It does not play well with Lexington’s alkaline soil, which can lead to leaves turning yellow and eventually trees dying.
That’s why it’s on the city’s “don’t plant” list for street trees. The University of Kentucky’s Cooperative Extension Service points to the pin oak problem to show how too many of one kind of tree can cause problems when a disease or harmful insect comes around. That is one of the reasons Trees Lexington doesn’t plant or give away red maples; there are too many already.
Most of the city’s once-dominant pin oaks are gone. Some of those remaining appear to be healthy, others still are dying.
The pin oak on Kilrush Drive used to be a street tree, but flooding from Wolf Run Creek forced the city to remove houses on its side of the street. On the city-owned greenway where the houses stood is the Kilrush Food Forest. That is an effort begun in 2020 by Nachie Braga and his company Geomancer Permaculture, working with neighbors, to remove invasive plants and install native plants, some of them edible. More information about the food forest is below.
More on pin oaks:
More on Kilrush Food Forest:
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