Liriope’s Muse: Tree Care Tips from a Master Arborist

The Science Behind Leaf Color

During spring and summer, leaves are green because of chlorophyll, the pigment that captures sunlight to fuel photosynthesis. As fall approaches, days grow shorter and the sun’s angle changes. This shift reduces the amount of light energy reaching the leaves, including high-energy gamma rays and other wavelengths. These energy changes signal to trees that it’s time to prepare for winter dormancy.

At the same time, cooler nighttime temperatures slow down chlorophyll production. With chlorophyll fading, other pigments that were always present in the leaf, carotenoids (yellows and oranges) and anthocyanins (reds and purples), are revealed. The balance of sunlight, temperature drops, and a tree’s genetics all combine to create the fall color palette we love.

Fall Color Changes in Houston

In Houston, some years pass without much of a fall color show at all, and the reason comes down to our climate. Because we often experience warm autumns with very few cool nights, the chemical signal that triggers leaf color change never really kicks in. Without a strong contrast between warm days and crisp nights, chlorophyll lingers longer in the leaves, masking the carotenoids and anthocyanins that would otherwise shine through. On top of that, sudden rainstorms, drought stress, or an early cold snap can cause leaves to simply brown and drop instead of gradually shifting through vivid shades. This is why one year your neighborhood trees may glow with color, and the next year it feels like we skipped fall altogether.

This year, though, I predict that the greater Houston area will experience a nice fall color change as we are already starting to see the early signs of color change and are expected to have a mild, but cooler than last year winter !

The Role of Gamma Rays and Temperature Drops

While gamma rays are part of the high-energy radiation from the sun, their intensity and seasonal fluctuations help regulate plant chemistry. Trees sense changes in the quality and strength of sunlight, which includes this radiation, and adjust their internal cycles accordingly. Think of it as nature’s timer telling the tree when to shift from growth to conservation mode.

Temperature plays an equally critical role. Warm, sunny days paired with cool, crisp nights are the perfect recipe for the brightest fall colors. The daytime warmth allows sugars to continue flowing into the leaves, while the nighttime chill slows their movement out of the leaves, fueling the production of anthocyanins, the pigments responsible for vivid reds and purples.

Why This Matters for Tree Health

The process of shutting down photosynthesis and dropping leaves isn’t just for show, it’s an essential survival strategy. By pulling nutrients back into their roots and branches before leaves fall, trees conserve energy and strengthen themselves for winter. Healthy, well-cared-for trees are better able to complete this seasonal transition smoothly.

For homeowners, this means that proper care throughout the growing season by watering, fertilizing, pruning, and protecting against pests, helps trees put on their best fall color display while ensuring long-term health.

Final Thoughts

Next time you admire the fiery reds of a maple or the golden glow of a hickory, you’ll know it’s more than just a beautiful scene. It’s a complex interplay of sunlight, gamma rays, and temperature shifts; a reminder that trees are living organisms finely tuned to the rhythms of nature.



At Eric Putnam BCMA, Inc., we love helping homeowners understand and care for their trees through every season. If you’d like advice on keeping your trees healthy year-round, our certified arborists are here to help. Schedule