Fall and Jack Frost

Word has it that Jack Frost prances around, pinching the leaves with his icy fingers.

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Word has it that Jack Frost prances around, pinching the leaves with his icy fingers. And this is what causes the leaves to turn in the fall. It’s not far off the mark. The shorter days and cooler nights trigger a corky membrane to grow between the branch and the leaf. This membrane interferes with the flow of nutrients to leaves.

Called the abscission layer, the corky barrier acts like Mr. Frost’s fingers squeezing out the color. What happens is the production of chlorophyll beyond the membrane becomes sluggish. The leaves then turn those famous fall colors. When the leaf no longer receives any nutrients, it’s released from the stem—into grand colorful piles on the ground.

Even evergreens go through a similar process. If you have pines, spruces and firs, you’ll notice many interior needles turn brown in the fall and drop off. These needles are two years old or older. In forests these needles create mulch and protection for seedlings through the winter.

Fall weather conditions that favor red and yellow leaves on deciduous trees are warm sunny days and cool nights between 45 and 33 degrees. Freezing can injure or kill leaves before the pigments reach their true brilliance.

If all this is too technical, just remember what the old wives had to say: A rainy day washes tree color away.

Seems good enough for me.