Weeds That Signal Your Soil Is Sour
Dandelions, mullein, sorrel, stinging nettle, and wild pansy all thrive in "sour" acidic soil (pH below 7.0).
If you find these pests in your garden, grow plants that also like their soil on the tart side: hydrangeas (whose flowers achieve their most beautiful shades of blue in acidic soil), blueberries, rhododendrons, and azaleas. In the vegetable garden, endive, rhubarb, shallots, potatoes, and watermelon all tolerate soil with a pH as low as 5.0.
Or, if you'd rather grow plants that thrive in neutral soils, you could raise your soil's pH by applying dolomitic limestone. To determine how much lime to use, send a soil sample to a lab for testing, then follow the lab's recommendations. Wood ashes also will raise soil pH, but don't use any more than 25 pounds per 1,000 square feet, and avoid applying them more often than every 2 or 3 years. Compost is a better buffer: Just add enough to raise your soil's pH to 6.5 or 6.8.
Photo: (cc) Bob Jenkins/Flickr