Oak leaf

Leaves Are Wearing Out

Have a look at the leaves of trees around you. Chances are pretty good that they don’t look healthy. Fading leaves with holes and other insect signs, mold and other fungi and a generally bedraggled look are normal at this time of year.  What is wrong with the tree? Probably nothing. Leaves look bad at […]

Persimmon fruit

Gender identity and the mystery of the persimmon fruit

What does gender mean? We know that human gender is a broad and fluid landscape within which people choose to identify themselves. This is increasingly recognized as a healthy and welcoming way to think about who we are. Gender fluidity is true in many animal species, perhaps the majority.  But what about plants? The photograph above […]

The second flush of growth

We think of summer as the “growing season” and we are used to our garden plants growing all summer. For most trees, though, growth takes place mostly in the early spring. Most trees in temperate regions produce a single flush of growth – the bud opens, leaves that were formed the previous year expand to […]

Lightning struck tree

Death of an Oak

This beautiful old oak tree was struck by lightning last September. Within 2 days, it had completely wilted and showed no signs of life. Sudden death due to lightning is uncommon in trees, especially after the end of the growing season. Several experts recommended leaving the tree until spring to see if it showed any […]

Holly leaf

A Question of Timing

Leaf exchange in holly We know that trees usually lose their leaves in autumn, which is why we sometimes call the season fall. A few trees do things differently, though. One of those is American holly, Ilex opaca. Holly is a tree that we usually call evergreen because it stays green year-round. But if you […]

Old chinkapin oak

The Wolf Trees of Nashville

When you hike through the woods in Nashville, you don’t expect to encounter wolves. If you keep your eyes open, though, you may see some wolf trees. Foresters used the term ‘wolf tree’ to indicate a very large tree with a broad crown and a short main stem.  These trees were considered wolves because they […]

Old oak tree

How Old is that Tree?

Everyone wants to know how old a particular tree might be. We will discuss this complicated and important subject in two stories. This month we will talk about unitary trees, and next month we will tackle the complex problem of aging clonal trees.   A unitary tree is like a person – a single, integrated organism. […]

Bur oak leaves

A Deep Green Autumn

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 […]

Quercus sumatrana in Sumatra

How many trees species?

When I worked in Borneo, I was fascinated by the immense diversity of trees in the jungles where I worked, even though I could only identify a few species. I did not even know how many different trees I was seeing. They look so much alike, with some exceptions, that I could walk by a […]

The Great Flush of 2015

Have you seen the Great Flush of 2015?  In Central Kentucky,  trees are growing very fast right now, producing new growth that is noticeable for its pale green or yellow colors.  Late flushes are complicated responses to changes in soil moisture. This is the first of several stories about the Great Flush of 2015, but […]

New leaves on a defoliated bur oak

A couple of weeks ago, we told you about a magnificent, ancient bur oak that was suddenly defoliated overnight.  We said that it would recover quickly and that we would update you. With 10 days of mild weather, the tree has leafed out very quickly.  Most trees maintain large reserves of starch and protein in […]

Showy flowers

Flowers, Pollen and Allergies

Is that tree causing your allergies?  That pretty tree with the white flowers?  That pine tree covering your car in green film?  Nope. It’s the trees you don’t see that are getting you. This is the height of allergy season. You can feel it in your sinuses and see it on your car windows. Huge […]

The Sap Is Rising

“The sap is rising” is an often heard description of early spring. If you cut into the stem or branch of certain trees – sugar maple, birch, hickory, walnut, or sycamore – on a cool spring day, you may see sap dripping from the cut end, or an icicle of sap forming.  The sap is slightly […]

Early Spring Trees

You may feel we are in the throes of winter, but for many trees, it is already early spring. How can that be? In the late summer, trees begin to enter a stage of deep sleep called dormancy. They don’t stop growing because it is cold, they stop growing because a combination of long nights […]

Why do trees hold on to their leaves?

Why do trees hold on to their leaves in winter?  We get asked this question quite often.  The short answer for the impatient reader is sex, or more specifically, puberty. In some years, cold weather comes on so suddenly that leaves are killed by frost.  Last year, a sudden cold snap came on the heels […]

Dead trees and what they can tell us

Dead trees are fascinating because they provide us with a permanent record of their lives. The annual rings that record the tree’s experience with drought, nutrients and temperature are familiar to most of us.  Somewhat less familiar, but easy to see, is the record of all the insults, accidents and stresses of life as a giant, […]

The plight of butternut

Butternut trees, Juglans cinerea, are beautiful relatives of the more common black walnut. They get the name ‘butternut’ from the rich, fatty nuts, which taste better than walnuts. Another name for the tree is ‘white walnut’ because the wood is lighter in color than black walnut wood.  You may already know butternut from eating its […]

Giant Cane in the Bluegrass

Giant cane, Arundinaria gigantea, was abundant in the Bluegrass before the area was settled. Bison herds maintained cane, grazing on it but then leaving for long periods, allowing the cane to recover. When bison were replaced by cattle, sheep and horses, the cane quickly disappeared. Natural stands of cane are today quite rare in the […]

A farewell to the autumn colors of ash trees

Ash trees, especially white ash, are among our most reliable and beautiful trees for fall color. White ash shows rich shades of red, purple, yellow and green, all within the same trees and the Biltmore ash variety is cloaked in yellow and orange hues. Green ash takes on an astonishingly bright yellow hue. Sadly, the […]

Leaves in a Warm Autumn

In a warm autumn, as we are having in 2016, leaf color change is slowed down. Instead of a quick display of color, we often see slow development of color, muted colors, and mottled colors within a single leaf. We had the same conditions in 2014. Trees use photoperiod, or day length, to determine when […]

Sassafras albidum in autumn

What is your favorite autumn tree?

What is your favorite autumn tree? Mine changes on a daily basis, but my current favorite has to be sassafras, Sassafras albidum. I like trees like sassafras and sweetgum that display many colors in a single tree. Sassafras is a great urban tree in fairly large spaces such as parks. It reproduces from root sprouts, […]

Ginkgo Trees Are Lovely – Let’s Stop Planting Them

Cities are heating up because of a combination of climate change, the urban heat island effect, and a loss of urban tree canopy cover. We can mitigate some of these effects and increase the resilience of urban environments  if we plant more trees. The wrong choice of trees, though, can reduce urban biodiversity and may […]

thousand canker disease

Death by a Thousand Cankers

We have posted a new article at Planet Experts, Death by a Thousand Cankers, about the tragedy of a new disease of black walnut.  Although not yet in Kentucky, is it present in surrounding states.  The disease is new and began in the western United States, where black walnuts have been introduced as ornamentals.  Since […]

Keep Growing Until We Have to Quit – The Yellow-Poplar Strategy

Trees are generally very conservative in their growth habits. They often go to extremes to avoid rare events such as an early frost or severe drought. This is especially true of shoot growth. Although we think of trees as growing all summer, most trees only grow in height for a few weeks. Flowering dogwood sets […]

Mower damage, old (O) and new (N)

Street tree abuse – Part II

Street tree abuse is our term for management of street trees that results in their death, or in severe damage that shortens their lives. We have previously shown examples of this throughout the Lexington area. Now, we show an egregious example of street tree abuse while it is happening. The scene is the Legacy Trail, […]