Eggshells usually end up in the trash without a second thought. But if you have a garden, those leftover shells can actually have a second life.

Eggshells are mostly made of calcium carbonate, and they contain small amounts of other minerals too. They can be added to soil, compost, and even used around certain garden pests. They won’t fix every garden problem overnight, but they’re an easy kitchen scrap to put to work.

Before tossing your next batch of shells, here are several ways you can use them around the garden.

Add Calcium to the Soil

Eggshells contain a lot of calcium carbonate, which can eventually add calcium to the soil as the shells break down.

Plants use calcium as they build new tissue and develop their cell walls. The catch is that whole or large pieces of shell break down slowly, so don’t expect a quick nutrient boost. Crushing the shells into small pieces or a powder gives them more surface area and helps them break down sooner.

Help With Blossom End Rot

Blossom end rot is the dark, sunken spot that can appear on the bottom of tomatoes, peppers, squash, and other fruiting plants.

It is associated with calcium availability, but adding calcium to the soil isn’t always enough to stop it. Inconsistent watering can interfere with a plant’s ability to move calcium where it needs to go.

Eggshells can add calcium to the soil over time, but keeping plants watered consistently is just as important.

Add Them to Your Compost

Eggshells are an easy addition to a compost pile or bin.

Crushed shells contribute calcium and other minerals to the finished compost. They don’t break down as quickly as fruit and vegetable scraps, so crushing them before adding them to the pile is a good idea.

Once the compost is ready, those minerals become part of the finished material that goes back into your garden.

Give Seedlings Some Extra Calcium

Young plants need a steady supply of nutrients as they develop roots, stems, and leaves. Finely crushed eggshells can be mixed into potting soil or garden soil as a slow source of calcium.

There is no need to add a large amount. A little goes a long way, and seedlings still need the full range of nutrients provided by good-quality soil or fertilizer.

Use Eggshells as Seed Starting Pots

Half an eggshell can make a tiny biodegradable container for starting seeds.

Rinse the shell, poke a small drainage hole in the bottom, add a little potting mix, and plant your seed. Once the seedling is ready to move outside, you can plant the shell along with it.

Crushing the shell slightly before planting can help the roots grow out more easily.

Add Texture to the Soil

Finely crushed eggshells can add some coarse material to soil, though they aren’t a substitute for compost or other organic matter.

If your soil is heavy or compacted, adding compost and organic material will usually do much more to improve its structure. Eggshells can still be mixed in as another way to reuse kitchen scraps rather than throwing them away.

Help Raise Soil pH

Because calcium carbonate is alkaline, eggshells can gradually raise the pH of acidic soil.

The change is slow, though, and the amount of eggshell needed depends on the soil. If you’re trying to correct a pH problem, a soil test is a much better starting point than guessing.

For a small garden, eggshells are best thought of as a modest addition rather than a replacement for garden lime.

Discourage Slugs and Snails

Crushed eggshells are often recommended as a barrier around plants bothered by slugs and snails.

The idea is that the sharp, uneven pieces make the surface unpleasant for soft-bodied pests to cross. In practice, the results can be inconsistent, especially after rain or watering.

Still, a ring of crushed shells costs nothing if you’re already saving them, so some gardeners like to try it around particularly vulnerable plants.

Add Calcium to Worm Bins

If you keep a worm composting bin, finely crushed eggshells can be useful.

Worms need calcium, and powdered eggshells can help supply it while also adding some grit to the bin. The shells should be crushed very finely so they can mix into the bedding rather than sitting around as large pieces.

It’s a small addition, but it’s another good way to put kitchen scraps to work.

Provide Calcium for Backyard Birds

Crushed eggshells can also be offered to backyard birds as a source of calcium, especially during nesting season when calcium demands can increase.

Bake or heat the shells first, then crush them into small pieces before putting them outside. This reduces the risk of leaving traces of raw egg behind that could attract unwanted animals.

A clean, shallow dish placed near your bird-feeding area can make the shells available to visiting birds.

Supplement Calcium for Backyard Chickens

If you keep chickens, eggshells can be recycled back to the flock.

Clean the shells, dry them thoroughly, and crush them into small pieces before offering them. Many backyard chicken keepers mix crushed shells into their hens’ feed or provide them separately.

Calcium is important for laying hens because they use it to produce strong eggshells. Oyster shell is another common calcium source for backyard chickens.

Keep Kitchen Scraps Out of the Trash

Perhaps the easiest reason to save eggshells is that there’s very little work involved.

Instead of throwing them away after breakfast or baking, rinse and dry them, then save them in a container. Once you’ve collected enough, crush them and add them to your compost, garden soil, seed-starting pots, or another garden project.

Eggshells won’t replace good soil, compost, fertilizer, or proper watering. But they are free, easy to collect, and useful in several small ways around the garden. That’s a pretty good second life for something that would otherwise end up in the trash.