A guest post by Elizabeth Matlin
No, eggshells are not an endangered species that we must rally around. But if you’re planting tomatoes in your garden this spring, you might want to start saving eggshells. Last year I ran across a newspaper article explaining that tomato plants grown in calcium-deficient soil experience more blossom end rot—a condition where a watery spot appears at the blossom end of the fruit and slowly enlarges, sometimes engulfing the whole tomato. Bell peppers, squash and watermelon are also susceptible. The article went on to say that spring rains deplete soil of calcium and that either crushed eggshells (made of calcium carbonate) or gypsum should be added to the soil when planting tomatoes, peppers, etc.
So between now and spring planting, shells from all the eggs I’ll be cracking for pancakes, muffins, cookies and Sunday morning omelets will be saved for my tomatoes rather than being tossed onto my compost pile. This is a great little task to assign kids. Just rinse out the eggshells and let them air-dry on a paper towel or plate at room temperature. Once the thick inner membranes lining the shells are dry and shriveled, place the eggshells in a plastic freezer bag, then place that bag in another freezer bag. (Eggshell shards are very sharp, so for safety reasons you need to use two heavier weight freezer bags as they will poke through lightweight bags.) Take a flat, firm object—I use a metal meat pounder, but the bottom of a firm plastic container will also work—and start crushing the eggshells. Let the kids pound away at them until they are the size of fine gravel—the finer the better. If you’ve ever composted eggshells, you know they take forever to decompose. But this also means your plants will have a great slow-release form of calcium all season. I use four to five crushed eggshells per tomato plant and mix them into the soil that fills the planting hole. Remember to ask the kids to help add the shells to the soil so they can see why they were doing all that pounding! I’m not sure if the shells from cooked eggs can be used, so if any chemists out there know whether calcium carbonate is altered by cooking, give a shout.