If you’ve been tossing whole eggshells into your garden, thinking they’ll quickly break down and nourish your plants, you might be disappointed. Growing Out The Box shares a video explaining that those shells can linger in the soil for years without breaking down. But with a few simple extra steps — cleaning, drying, and grinding — you can turn them into a powerful soil booster.
Here’s why this small change can make a big impact in your garden.
Whole Eggshells Take Their Time to Break Down
Tossing eggshells into the garden seems like a great idea, but they don’t break down as quickly as you might think. A four-year test from Garden Myths found that even after years in the soil, eggshells remained largely intact. This means they don’t release much calcium right away, making them less useful as an immediate soil amendment. If you’ve been adding whole or coarsely crushed eggshells expecting quick results, you might not be seeing the benefits you hoped for.
Grinding Eggshells Unlocks Their Nutrients
For plants to actually benefit from eggshell calcium, the shells need to be ground into a fine powder. A coffee grinder works well for this — just make sure the shells are clean and dry first. Research from the University of Illinois Extension found that finely ground eggshells can be just as effective as commercial calcium supplements for improving soil health. This is especially helpful for plants like tomatoes and citrus trees, which need extra calcium to prevent issues like blossom end rot.
A Boost for Earthworms and Soil Health
Beyond plant nutrition, ground eggshells support the tiny workers that keep soil healthy — earthworms. These creatures rely on gritty materials like eggshells to help them digest organic matter. Red Worm Composting notes that adding ground eggshells to a worm bin can even boost reproduction, leading to a thriving worm population. More worms mean better soil aeration and nutrient cycling, which benefits your entire garden.
