KC Gardens

Why are there leaves still stuck on the trees? There’s a word — and reason — for that

What’s up with the tree leaves? Have you noticed they’re still hanging on?

Many trees have a full canopy of the leaves that appear dried but aren’t falling. This is because we are experiencing a condition known as a marcescence, which means to wither without falling.

Remember a few short weeks ago when we experienced one of the most beautiful periods of fall color ever in Kansas City? We witnessed bright hues of red, orange, yellow and maroon rarely seen in our area.

This outstanding fall color was a result of timely September rains, warm days and cool nights mixed with plenty of sunshine. This combination built up high levels of sugars in the leaves, stimulating the production of the compounds that created the fall color. What an enjoyable period that was as we marveled at the beauty of nature.

When the first cold front of the season arrived, the excellent fall color came to a screeching halt.

Gone were the mild days and cool nights. Instead, the temperatures quickly plunged into the single digits.

This rapid drop followed by record lows stopped the natural processes that cause the leaves to drop — marcescence. The leaves hang on because they did not have a chance to form what is called an abscission layer.

The layer refers to cells that form at the point where a leaf attaches to the branch. As this layer forms in the fall, it stops the sugars from exiting the leaves resulting in the wonderful color. If this layer does not properly develop, then there’s usually neither fall color nor leaf drop.

Look around your neighborhood. Many of the trees still holding onto their leaves have a dull, dry green appearance. Oaks, smoketrees, some maples, sycamores and pears are good examples. Shrubs, such as viburnum, will also be marcescent. The cold weather froze the process and now these leaves are attached without a way to fall.

Is there a downside to this rare condition?

One issue will be the never-ending task of leaf cleanup. The leaves will eventually drop based on weather conditions. The weight of rain or snowfall will help them to fall. A strong gust of wind will also speed up the drop.

The greatest concern is a heavy, wet snow or ice event. The added leaf surface will hold the moisture, increasing the weight of each branch. The result could be limb breakage, which could lead to power outages.

Is there anything you can do? Not really. Just wait it out. By spring, when the new leaves start to emerge, the leaves will be gone.

For now, we can add a new word, marcescent or marcescence to our vocabulary.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Got a question for him or other university extension experts? Email them to garden.help@jocogov.org.

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