It happens every summer.

By Steve Bender
Yellowing Hydrangea Leaves
Credit: Steve Bender

People love to be frightened. Without impending doom, imminent catastrophe, horrific threat, or looming disaster, life seems utterly prosaic and quotidian. (I've been waiting years to put those two adjectives in a column! Translation: humdrum and boring.)

Thus, it comes as no surprise that nervous gardeners email me by the dozens every August concerning the certain demise of a favorite tree and shrub, as indicated by leaves turning yellow and dropping. Should I spray, water, fertilize, or mulch, they plead, or perhaps stop doing any or all these things?

My response is devastating. "Not to worry," I say. "This is normal."

Oh noooooooooooooooooooooooooooooooooooooooooooooooooooo!!!!

See, woody plants in the temperate world go through several stages each year – a growth stage, a resolution stage, and a dormant stage. The growth stage starts in spring and continues through most of summer. Plants take advantage of abundant water and favorable weather to grow lots of new leaves and branches. By mid-August, though, they're transitioning to a resolution stage. They stop growing, consolidate their gains, and try to keep from dying until they go dormant. This is a good thing, because in most places in the South, August and September are dry months, but still hot.

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The resolution stage means trees and shrubs don't need as many leaves as before. More leaves just mean more water loss at a time when growth has slowed or ceased. Plus, many older leaves have suffered damage from sunlight, heat, wind, storms, and pests during the growing season. So the production of green chlorophyll stops in those leaves, revealing the yellow and orange pigments that were there all along. Even though it isn't fall yet, leaves turn color and drop – just like is happening with my hydrangea, above. Early leaf drop is especially common with tulip poplar, river birch, Yoshino flowering cherry, and buckeyes.

I hope this post hasn't made YOUR life prosaic and quotidian. Even though you have one less thing to stew about, the garden always provides more! Like those webs filled with caterpillars that are consuming your pecan tree or the squirrels plucking every ripe tomato. It's a war out there, soldier!