I heard that putting crushed eggshells on flower beds is good for plants. What’s the best time of the year to do this? —Karen Beasley, Marshall, NC
I’ve heard this, too, but colleagues who study fertilizers and soil science say that eggshells are slow to break down and yield small amounts of calcium. Incorporating crushed eggshells does raise soil pH, and is most valuable when you’re gardening in acidic soil. Coincidentally, those low pH soils tend to be low in calcium, which is another reason the eggshells could be beneficial.
Bottom line: It doesn’t matter when you spread the eggshells. They’ll hang around a long time before their nutrients become available to the soil and affect the plants. Crush the shells as finely as possible for the quickest breakdown.