Q. How can I clean off the whitish crud that inevitably builds up over time on terra-cotta pots?
A. Clay pots help keep soil moist but not soggy, they insulate plant roots against overheating in the summer, and their warm reddish color combines attractively with many flower and foliage hues. Their porous nature lets them hold air and water to the benefit of the plants growing in them, but it also provides spaces where deposits of calcium, minerals, and salts from fertilizers can become trapped. As moisture in the terra-cotta evaporates, these residues are wicked to the surface of the pot, where they accumulate in whitish streaks and bands. Some gardeners appreciate—and even encourage—the resulting aged look this gives their pots, but it’s not for everyone or for every garden’s decor.
To rid pots of crusty residues and clean them up for future occupants, Minnesota gardener Amy Andrychowicz, author of the Get Busy Gardening blog, recommends a combination of scrubbing and soaking, followed by a disinfecting trip through the dishwasher.
1. First, use a brush to remove as much loose dirt as possible from the pot’s surface. No fancy equipment is necessary, says Andrychowicz—an inexpensive (albeit unused) toilet brush or other household scrub brush will do the job.
2. Once the superficial soil is brushed away, submerge the pot in a 20 to 25 percent vinegar solution (1 cup 5 percent acidity white vinegar in 3 or 4 cups water) for 20 to 30 minutes. “The less vinegar you use, the longer you’ll need to soak the pot,” Andrychowicz says. “You may hear sizzling sounds or see bubbles rising,” she adds. “Don’t worry, that’s the vinegar doing its job of dissolving the buildup.”
3. If the buildup wipes or scrubs off easily after the soak, the pot is done. Otherwise, soak a while longer, checking occasionally until all of the residue is easily removed. “You may need to use your brush to scrub it off,” Andrychowicz says. For really tough residues, such as around the rim of a pot, she uses undiluted vinegar to loosen them up. She recommends following a soak in pure vinegar with a soak in clear water to dilute the vinegar the pot absorbed.
4. Finally, Andrychowicz runs her pots through the quick-wash cycle of her dishwasher to disinfect and clean them before she fills them with fresh potting mix and new plants. “Or you can simply scrub them in soapy water,” she adds.
Originally published in Organic Gardening Magazine, December 2013/January 2014
Photos: Patrick Montero