It’s autumn, the season for leaves, nuts, needles, and other arboreal detritus. They pigment briefly, reminding us that summer really is over, before dropping their foliage. Then the usual nuisances apply: raking and bagging, then raking and bagging again, and maybe even again. Depending on the type of trees, the quantity of rainfall they enjoyed during the late summer, and current weather conditions, your leaves might fall all at once or over a period of many weeks.
I live in Atlanta, the “city in a forest.” Evergreens are common, but also the deciduous trees that make autumn into fall. Magnolia, hickory, poplar, dogwood, oak, birch. The magnolias are ornery; they hold onto much of their foliage in autumn and instead drop their thick, hearty leaves in spurts during spring.
But it’s the oaks that cause the most trouble. There are so many of them here, and they are so stately, rising 40 to 80 feet in height when mature. That’s a lot of leaves. And the oak’s leaves and its distinctive acorns contain a surplus of tannins, which easily stain stone and concrete sidewalks, driveways, and walks if left to decompose.
Among those who dwell under oak canopies, the experienced will learn to sweep, rake, or blow the leaves and acorns off of porous surfaces quickly. But even the vigilant can’t keep up with nature. When dropping leaves are accompanied by rains (and the winds that help them fall), immediate cleanup becomes impossible.
Worse, the rain helps seep more tannins out of the leaves and especially the acorns, creating strips of stained pavement where water flows down a grade. So many shades of rust, from ruddy to alloy to burnt to russet to umber. The tannins in red wine are what make its stains so hard to get out; acorns are the cabernets of autumn.
There are solutions, none perfect. Everyone should have a pressure washer—but that’s an object lesson for another day, and plain water probably won’t help anyway. Some try to bleach their drives, but the runoff risks harming plants and probably creates even more unsightly blotches anyway. Rust removers like oxalic acid or CLR might work, but applying these chemicals to large areas is impractical. A 20 percent solution of hydrochloric acid is another option, but it’s corrosive and highly poisonous. Anyone with kids or pets might think twice, and that’s probably most everyone with oaks to worry about.
There’s another choice. Sunlight will fade the stains over time, and other stains of other sorts will even and deepen the patina of the pavement. The oaks, decades or centuries old, rise high above your silly little house with its leaf blower whining in vain. They are here to remind you that nature is bigger than you, and your driveway, and your pride.