How to Use Eggshells in Green Gardening

Medically Reviewed by Jabeen Begum, MD on November 07, 2022
4 min read

Folks have tried putting crushed eggshells in their gardens for all kinds of purposes: to act as mulch, to feed plants, to stop weeds from growing, and to keep pests away. Most of those ideas don't work, but eggshells can be useful in your garden if you prepare them properly. And while eggshells compost slowly, they will eventually break down and add nutrients to your compost. There are also ways to help eggshells compost faster, including drying and crushing the shells before adding them to the compost bin.

Don't compost the inside of the egg — the yolk or the white — because it may draw rodents and flies. Rotting eggs can also make your compost pile stink. Crushed eggshells, on the other hand, make great compost material.

Why compost? Composting is a staple of green gardening. It's a great way to recycle kitchen scraps, keeping food waste out of landfills. You can toss food scraps like eggshells in a backyard compost bin along with fall leaves, twigs, straw, or wood chips. Or you can add your kitchen waste to a worm bin and let red wigglers turn your trash into compost treasure. When the compost is ready, you can use it as a natural fertilizer in place of store-bought chemicals.

Why are eggshells good for compost? Eggshells contain lots of calcium and other nutrients plants need. If you use a worm bin to compost, ground eggshell can also help your worms digest the other food scraps in the bin. Worms, like chickens, use grit to help grind up their food, and ground eggshell works well for this purpose.

Can eggshells add salmonella to your compost?Salmonella bacteria are sometimes found in eggs and can make people sick. But cooking eggs kills salmonella, and so will the heat in your compost bin. Finished compost (even if it contains eggshells) usually has a similar amount of salmonella to the rest of the soil in your yard.

You can crush your eggshells by hand and toss them into your compost bin. Eggshells do take longer to break down than most other food waste, so your finished compost may have bits of eggshell in it. That's okay — the eggshell will finish breaking down in your garden — but there are a few ways to make eggshells compost faster.

Grinding. Eggshells compost slowly because of the calcium content in the shell. Large pieces of eggshell take a year or more. But the smaller the bits of eggshell, the faster they will compost. To really speed up the process, turn your eggshells into powder by crushing them in a coffee grinder. If you use a coffee grinder to make ground coffee, buy a cheap coffee grinder just for your eggshells.

Drying. Whether you intend to use a coffee grinder or smash your eggshells by putting them in a plastic baggie and stomping them into bits, drying eggshells out first will make them easier to crush. Set them out to air dry for a few days. Or spread them on a cookie sheet and place them in a warm oven to make them dry more quickly.

Boiling. If you have lots of eggshells, you can make a liquid fertilizer. Boil 10 to 20 eggshells, then let the pot sit out overnight. Strain out the eggshells the next day. Water each plant with up to 2 cups of the liquid, as often as every two weeks.

If you use the coffee grinder method described above, you can add the ground eggshell directly to your garden. If soil tests show that your soil needs more calcium, spread ground eggshell on your garden and landscaping. When you plant tomatoes, put powdered eggshell in the planting holes.

Blossom end rot happens when the fruit of a plant doesn't have enough calcium in it. The end of the fruit opposite the stem rots, leaving you with less produce to enjoy. Blossom end rot occurs in:

  • Tomatoes
  • Peppers
  • Eggplant
  • Squashes (like zucchini)

Gardeners sometimes say you should add crushed eggshells to the planting hole when you place these plants in your garden. But does that really work? If you don't grind the eggshell into powder, as explained above, the eggshell pieces won't decompose fast enough to do your plants any good. But if soil tests show that your garden soil does lack calcium, adding ground eggshells to the soil could help prevent blossom end rot.

On the other hand, if soil tests show that your garden already has enough calcium, the problem may be too much or too little water or root damage. If the plant can't get the calcium from the soil to the fruit, it can still suffer from blossom end rot. Focus on even moisture around the plant. Don't water too much or too little, and mulch around the plant to hold moisture in. Avoid digging within 1 foot of the plant's stem so you don't damage the roots.

Slugs and snails eat leaves, flowers, and fruit and can cause a great deal of damage in your garden. Some people have tried to get them to go away by spreading crushed eggshell around plants. The idea is that the sharp points of the eggshell pieces would hurt them as they crawl toward the plant. But studies have shown that eggshells have little effect on slugs and snails. Instead, you can try:

  • Switching from sprinklers to drip irrigation
  • Trapping and killing slugs and snails
  • Setting up copper barriers around the bases of plants

While there are some myths about what eggshells can do for your garden, powdered or boiled eggshells can add calcium and other helpful nutrients to your compost or garden soil. Even if you decide not to grind them, composting is a great way to recycle your eggshells and help your garden in the long run.