Fall Colors and How They Get That Way
By Cindy Bellinger It's been a long, warm fall and some leaves have been slow to change. Still, the colors this autumn make a dazzling display. Changing colors are a result of diminishing daylight and cool nights with temperatures between 45 and 33 degrees. The Chemistry of Autumn
The chlorophyll in leaves is very unstable and oddly it's bright sunlight that causes it to decompose. To maintain their green-ness, plants constantly need to produce chlorophyll. One of the primary triggers for chlorophyll production is warm temperatures. When nights begin cooling, green begins leaving. What's left when chlorophyll disappears are the sturdier pigments such as carotene, xanthophyll and anthocyanin. Yellow Leaves
When chlorophyll fades and exposes carotene and xanthophyll, the leaves appear yellow or orange--as with cottonwoods and aspens. Red Leaves
When chlorophyll fades and exposes anthocyanin, the leaves are pink, red or purple--as with maples, sumacs and Virginia Creeper. Brown Leaves
When chlorophyll fades and exposes tannin, the leaves are brown--as in oaks. Falling Leaves and Jack Frost
Along with the weakening chlorophyll, the cooling nights triggers a corky membrane, called the abscission layer, to grow between branches and leaf stems. This film also interferes with the production of chlorophyll. And this ushers in Jack Frost, who is rumored to run around with icy fingers pinching the leaves and making them fall. But it's really because the leaves no longer receive nutrients that they're released from the stem. Likewise on Evergreens and in Your Garden
If you have pines, spruces and firs, you'll notice many interior needles also turn brown in the fall and drop off. These needles are two years old or older.
So this is what's happening chemical-wise in your garden as well. It's a lovely fall even if the weather is a bit odd this year. Read My Little Garden Patch - gardening column by Cindy Bellinger.
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