Some years it seems like the leaves never really change color in North Florida and then there are other years where they are a rainbow of color. Why is that? It really has to do with a combination of factors that include the quantity of sunlight, lower air temperatures, moisture, and plant physiology.

Natural Pigments

Plants produce energy through the process of photosynthesis. This process uses sunlight and chlorophyll to make energy. In the fall some plants naturally make less chlorophyll as a response to cooler air temps. Chlorophyll is the pigment that make leaves green. As the plant produces less of those, the green color goes away. The plant then moves the remaining chlorophyll in the leaf into reserves for the spring. As a result, you can begin to see other pigments that are present which include carotenoids (yellow and orange color). This is true for plants with yellowing leaves. If the leaves have a red undertone, then that is from anthocyanin pigments. These pigments produce the red, purple, and pink colors in leaves. Research shows that this pigment is produced in some plants when chlorophyll is broken down. It is believed by scientists that it acts as an antioxidant because the breakdown of chlorophyll can produce toxic by-products and also provides some sun protection to the leaf before it falls. By protecting the leaf, it is thought that the plant can more easily move nitrogen back into reserves to use later. The changing of leaf color is a dynamic process that is different depending on the plant species, climate, and location. The leaves finally produce tanins, which turn the leaves brown and fall from the plant.

Color in North Florida

In North Florida, the most reliable trees to provides some fall color include deciduous trees like maples, cypress, and sycamores. Depending on the species tends to depend on the variability of the leaf color on one plant. For instance, a red maple may have huge variability in the color of the individual leaves. This is dependent on the amount of anthocyanins present and the percentage they are mixed with carotenoids or chlorophyll. Anthocyanins mixed with chlorophyll tend to have a brownish hue while leaves with more anthocyanins and carotenoids have a more orange hue. The sooner the air temperatures dip, the sooner the leaves will change color. That is why some years the leaves will change early in the season and have better color.

References

Lee, D. and O’Keefe, J. 2004. Autumn Foliage Color. https://harvardforest.fas.harvard.edu/autumn-foliage-color

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