Q: I saw online that you can put crushed egg shells in the soil around tomatoes for extra nutrients. Is this a good idea?
A: It doesn’t hurt anything to put crushed eggshells around tomato plants, but it probably doesn’t benefit them much either. Garden experts, including me, once believed that extra calcium for tomatoes is needed to prevent blossom end rot. This has been demonstrated to be incorrect. Blossom end rot is caused by fluctuations in soil moisture that result in calcium not going to the young fruit at the right time. There could be plenty of calcium available in the soil but if it is not transported quickly to developing tomato fruit, the blossom end turns black, thereby ruining it. There is no harm done by adding egg shells, coffee grounds, or banana peels under your garden or landscape plants. But these are in no way magical substances that give the plants any advantage.