How to Use Eggshells in the Garden

Chicken eggshells are commonly used in gardening due to their high calcium content. For humans, calcium helps to build and maintain strong bones, which form the structure of our bodies. Similarly, calcium assists in plant growth by providing structural support for cell walls.

Eggshells are made of calcium carbonate, a substance also found in agricultural lime, snail shells, seashells, and pearls. Agricultural lime is a soil additive used to increase the pH of acidic soil, provide calcium for plants, improve water penetration, and improve plant absorption of other nutrients. Some gardeners see eggshells as a low-cost, natural alternative to products like agricultural lime. In addition to calcium, eggshells can also be a source of magnesium, phosphorus, and potassium. These nutrients come from the thin outer membrane of the egg.

Using eggshells in the garden isn’t just a great way to keep kitchen scraps out of the landfills—it may benefit the soil.

• Increase calcium levels: Due to their high calcium content, eggshells may improve your soil’s calcium levels over time. Eggshells take some time to break down, so the smaller particle size, the faster you’ll see results. Before using eggshells as a soil amendment, test your soil to see if you have a calcium deficiency.
• Improve aeration and drainage: Finely crushed eggshells can create small holes in the soil, improving airflow and drainage in compacted soil. Water, air, and nutrients will have better movement through the soil and access to the plant roots, producing stronger plants.
• Reduce acidity: Some plants, such as radishes, can thrive in acidic soil, but many plants prefer soil with a more neutral pH. Test your soil’s pH and research your plants’ needs before making adjustments to the pH levels. Finely ground eggshells mixed in with garden soil may help neutralize acidity, but they’re not a quick fix: It can take years for the calcium in eggshells to break down.

Before using leftover eggshells in your garden, rinse them with cool water and let them dry out completely. Removing any trace of egg white will discourage critters from snacking on your eggshells. A thorough rinsing should be enough to clean them, however, some gardeners also place them in the oven for a few minutes to kill any salmonella.

1. 1. Compost: The easiest way to use eggshells in your garden is to add them to your compost bin. Keep in mind that the smaller the eggshells are ground, the quicker they will break down. If you’re not concerned with shards of eggshell making their way into your vegetable garden, simply crush rinsed, dried eggshells into small pieces with your hands. For faster results, grind the eggshells into a fine powder using a coffee grinder, rolling pin, mortar and pestle, or blender.
2. 2. Soil additive: If you don’t have a compost pile at home, you can still use eggshell powder to amend your soil. Simply sprinkle ground eggshells onto your soil, or mix them in with potting soil or fertilizer.
3. 3. Mulch: Some gardeners like to use clean, ground eggshells as mulch. Although it may take a lot of eggshells to cover an entire garden, mulch can help suppress weeds and retain soil moisture.
4. 4. Seed starters: Try using eggshells to start seeds. This can be a fun DIY project for young gardeners. Clean eggshell halves and fill with potting soil and seeds. Choose herbs and other small plants that don’t require space for deep roots. Place the seedlings in a sunny window and keep the soil moist. Once the seedlings show true leaves, transplant to a larger container.
5. 5. Chicken feed: If you keep chickens, simply recycle your shells back into your chicken feed. It might seem weird, but birds actually need the extra calcium to produce their own eggs. If you don’t keep chickens, try mixing eggshells into the bird food in your bird feeder.
6. 6. With coffee grounds: If you want to raise the amount of nitrogen in your soil while keeping acidity levels low, try mixing used coffee grounds and finely ground eggshells into your fertilizer or compost heap. The coffee grounds are high in nitrogen while the eggshells may help with absorption.

Although eggshells may have some benefits in the garden, they won’t solve every gardening issue.

• Eggshells do not kill slugs. Some gardeners theorize that sharp edges of eggshells may work as a natural pesticide against slugs and other soft-bodied creatures, but there is no evidence that eggshells actually work as pest control.
• Eggshells are slow to break down. It can take several months, or even years, for eggshells to completely break down. Finely crushing the shells before adding them to compost or soil can help speed up the process, but don’t expect overnight results.
• Eggshells do not prevent blossom end rot. Blossom end rot can be a sign of calcium deficiency in tomato plants, but it doesn’t necessarily signal that your soil is low in calcium. Blossom end rot is more often caused by erratic watering, which makes it harder for plants to transport nutrients like calcium through their systems.
• Eggshells can interrupt root systems. Make sure that any eggshells beneath the soil surface are finely ground. If not, the large pieces can interrupt root growth.

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