After Bad Drought & Heat, Why Is Fall Color So, So Vibrant?October 3rd, 2012 at 2:38 pm by Chad Evans under Chad's WLFI Weather Blog
Wow, the fall color is looking great! The pinks, reds, oranges & purples really look bold this year. Why after such a stressful year for trees? There are several reasons:
1. We had a record number of sunshine hours from spring to late summer. There were so many mostly sunny to sunny days that UVB/UVA protecting pigments in the leaves were upped this year. The oranges & pinks we see are the sunshine-protecting agents in the leaves. When it gets cooler & daylength decreases, it signals the tree to stop producing chlorophyll (green pigments used to collect sunlight). So, the tree stop producing chlorophyll & underneath the chlorophyll are the colorful pigments. These colorful pigments accomplish the job of melanin in our skin. Melanin in our skin makes our skin darken in sunlight (tan). These pigments are antioxidants against the sun to trees. That is why eating plant leaves (spinach, lettuce, etc.) is so good for you. You are ingesting those antioxidants.
2. It was a very dry, hot summer. This added stress sharpens pigments. It is sort of like melon farming. You want rain at first to get the melon to swell & grow, but then you want the fruit to stress a bit at the end. This dry weather stress actually ENHANCES the flavor by cutting down on water in the fruit a hair & concentrates the sugars & antioxidants. This is why California produce is so good. You can irrigate your orchards, then in the hot, dry summer, you can turn it off at the end & the hot, dry days actually enhance the sugar content of the fruit. Problem is, when it is shipped a long distance, this flavor goes down.
3. We received the rains at the right time. Despite the hot, dry, droughty summer, abundant rainfall since August has helped the trees a lot. They are no longer stressed overboard. It it is too dry the leaves wither & fall off. This year, its just right with the sun, drought & now nice, nice rains!
4. We continue to get a lot of sun. Sunny days just enhances the color even as it changes.
5. Notice how you don’t know whether to run air conditioning or heat? During the day it has been warm, but at night, since early September, we have seen huge drops (as much as 35 degrees). These big drops with crisp, cool nights, enhances temperature-protecting mechanisms in the leaves. This slight stress enhancing color.
Actually, cloudy, warm, humid weather with rain is bad for fall color. Cloudy skies causes trees to cut back on protective pigments in the leaves & persistent water on leaves causes fungal issues than puts unsightly spots on the leaves & makes them all off prematurely.
Addingly, a windy fall can cut the fall color season for obvious reasons, as the leaves blow off early.