A few years ago, I wrote about using horticultural vinegar to kill weeds. At a recent Deale Farmers’ Market, a customer who bought peaches from me insisted that my recommendation to use vinegar does not kill weeds. She even went to the trouble of boiling the vinegar, thinking she would be concentrating it. What she did not realize is that boiling vinegar dilutes the acetic acid, which is why vinegar gives off a strong odor when heated. Regular cider vinegar or white vinegar contains only...