KC Gardens

Fall color is better than expected

Fall color

Tip of the Week

If you would have asked me a month or so ago to predict the fall color outlook I would have said, “Marginal at best.” The terrible heat and drought of this past summer took their toll on the trees and shrubs. Many were/are stressed to the max, and the leaves on many plants appeared burnt to a crisp. But over the past week or so I have been pleasantly surprised by the early fall color.

I have noticed in my neighborhood a wonderful display of clear bright yellows on the green ash and the delightful purples are making a show on the white ash. The red maples are turning a nice red. Is this an indication of things yet to come?

Normally the peak color for the Kansas City area is around the third week in October. But over the last few years the peak has occured later and later. Could this be the changing climate at work? Peak color for KC this year could be the fourth week in October, or maybe even later. That, of course, like so many other things, is weather dependant. It is helpful to understand how and why leaves change color each fall at seemingly the same time of year.

The best hope for a colorful display is when the conditions are favorable for a so called “Indian summer.” That is a weather pattern of clear, sunny days with a combination of cool, crisp nights. This type of weather allows for the development of the pigments responsible for the yellows, oranges and reds we typically like to see. So far, October has experienced almost the perfect weather conducive for early fall color.

Not all factors are completely understood, but we do know it is a complicated process involving the interaction of sunlight, moisture, temperatures, daylight, the genetic traits, and chemical compounds and hormones found in the leaves.

A good place to start with how leaves change color is to understand why they are green. Leaves are green because of the presence of chlorophyll. Chlorophyll is plentiful in leaf cells during the growing season. Because of its high levels, the green color masks and dominates the other pigments that are present, thus giving the leaf its green color. Remembering junior high science, chlorophyll is used in the process of photosynthesis, where the leaf traps the sun’s energy and uses it to make sugars from water and carbon dioxide. It is these sugar compounds that nourish the tree.

During the summer months the tree keeps producing high levels of chlorophyll. But by fall’s arrival these reserves are depleted and slowly the green mask recedes revealing the other pigments in the leaves, which provide the color display.

The two most common pigments in leaves are carotenoids and anthocyanins. Carotenoids give us yellow, brown, orange, and many of the hues in this color palate. Anthocyanins develop reds, purples and their blends, which are the more prized coloration for fall leaves. The carotenoids are present in the leaves all summer long, while the anthocyanins develop in late summer from the breakdown of sugars. It is the Indian summer conditions that increase this pigment formation. This helps explain why more tree species turn yellow in the fall instead of red.

There are many locations around Kansas City to get your fix for fall colors. The bluffs along the rivers provide some of the best shows, while many older residential streets offer a mix of hardwood species to provide spot color. We also need Mother Nature to cooperate and provide us with sunny days and cool nights. A hard freeze would put an end to the miracle display of nature and science taking place in the ever-changing leaves. Even though this past summer’s stress is now a distant memory, it would be great to finish the year with a wonderful display of fall foliage.

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