Gardening 101: How to Use Eggshells in the Garden
May 28, 2019· Gardening 101: How to Use Eggshells in the Garden. ... Composed of calcium carbonate, eggshells are an excellent way to introduce this mineral into the soil. To prep the eggshells, grind with a mixer, grinder, or mortar and pestle and till them into the soil. Because it takes several months for eggshells to break down and be absorbed by a plant ...