While you can put eggshells in your compost bin, you may have heard that you can just put the shells straight into a plant’s soil instead to act as a natural fertilizer. But does this really work, and are eggshells good for plants at all? The short answer is yes and no, depending on how you prepare the shells and which plants are involved. Here’s what you need to know, according to an expert.
Paris Lalicata is a plant education and community engagement associate at The Sill plant shop based in New York.
Do Eggshells Provide Plant Nutrients?
Eggshells contain calcium, which is a key nutrient for many plants. That doesn’t mean you should just crumble eggshells and toss them into your monstera’s pot. “You can’t just throw eggshells in the soil and give your plants calcium that way,” says Paris Lalicata, plant expert at The Sill. “Eggshells take a long time to break down in the soil and make the calcium available to plants, so it’s not a quick fix for plant nutrition.”
Eggshells are best used in outdoor gardens, rather than for houseplants, because conditions are more favorable for breaking down the shells.
Garden plants like tomatoes and citrus trees benefit from additional calcium to strengthen their blossoms and fruit. Most houseplants don’t usually need extra calcium. They get enough calcium and other nutrients from an all-purpose potting mix. “It’s not beneficial for anyone to be putting eggshells in their potted plants,” adds Lalicata.
How to Use Eggshells for Plants
If you decide to add calcium to your plants with eggshells, grind the shells into a fine powder using a coffee grinder, Lalicata says. Don’t crumble them by hand. Eggshells decompose very slowly, taking more than a year to break down outdoors, so most of their calcium is locked in the shell and unavailable to feed plants. Grinding the shells into a fine powder helps the calcium get into the soil and the plant faster.
A study found that finely ground eggshells performed as well as pure calcium when it came to adding this nutrient to garden soil and it outperformed agricultural lime. The study also found that eggshells crushed by hand “were not much better than nothing at all.”
If you don’t want to go to the trouble of grinding up eggshells for your plants, you can just toss the shells in a compost bin where they’ll slowly break down into a form that plants can use. “The calcium in the shells is released into the compost,” Lalicata says. Adding the compost to plants will provide far more benefits than just adding the shells.
Other Ways to Provide Calcium to Plants
If a soil test reveals your soil is deficient in calcium, there are better ways to add this nutrient than crushed eggshells.
- Foliar calcium sprays are the fastest way to give calcium to a plant. Spray it on the leaves, and the plant absorbs the nutrients immediately.
- Agricultural lime boosts calcium in soil and raises its pH, making it less acidic. Lime is also known as calcium carbonate.
- Bone meal releases calcium at a slower rate than lime and doesn’t raise the pH as much as lime.
- Wood ashes add calcium to your soil without raising the pH.
- Gypsum is a fast-acting calcium supplement that does not affect soil pH.
