Add half eggshells and crushed eggshells to compost bin with worms. Often one may find baby worms curled up in the half eggshells.
Place half eggshells in egg carton and fill each shell with soil. Plant a seed in each. When time comes to transfer the plant into a pot or outdoors, place the plant with the eggshell directly into the new soil.
Sprinkle crushed eggshells around plants. It will help to keep away slugs since they do not like to go over sharp surfaces.
Eggshells break down slowly and provide calcium for plants to absorb. If you add finely crushed eggshells and mix into the soil every year, the ground will become more calcareous. Sweet peas and hibiscus, for example, thrive in chalky soil. Beets, cabbage, and spinach are also suitable.
Mix left over brewed coffee or coffee grounds mixed with water or soil for plants that thrive in acid soil, such as roses, rhododendrons, blueberries and tomatoes.