You’ve probably seen a post or two on social media at some point praising the ability of eggshells to add to calcium to soil. It’s true that eggshells are mostly made of calcium, and calcium plays a big role in determining the soil’s pH— a measure of a soil’s acidity or alkalinity—and an important factor in plants’ overall health.
You Might Want to Rethink Putting Eggshells in Plants
Here’s the thing: While eggshells can be beneficial for soil, it’s a slow burn. They take a long time to decompose, and crumbing them up and sprinkling them on top of the soil of your potted plants is not really going to do them any favors. It won’t hurt them, but it’s probably not going to help in any meaningful way.
Moreover, it’s pretty unlikely that your houseplants even need extra calcium because pH really isn’t an issue for potted plants. Potting soils have a pH that is close to neutral, so if you’ve repotted your houseplants at any point in the last few years, the soil is probably well-balanced already. And even if you haven’t, lack of calcium doesn’t come close to topping the list of reasons your houseplant might not be thriving. (Light and water are at the top of that list.)
The only way to really know if your soil is too acidic is to do a pH test. If you do test your soil and find out that you are actually dealing with soil that’s too acidic for the plants you are growing, you’ll want to add ground limestone, which will take care of the problem much more efficiently than crushed eggshells.
But that doesn’t mean saving eggshells from the garbage can is completely pointless. Here are a few other ways you can put them to good use.
If you want to sprinkle your eggshells out in your compost pile, where they can break down slowly (and where an abundance of microorganisms can aid in the process), go for it. Eggshells can add a valuable amount of calcium to the soil over several seasons. What they can’t do is fix a calcium deficiency quickly, or keep your houseplants from wilting.
You can use eggshells as cute (and free!) little vessels to start vegetable seeds in spring. If you want to transplant your starts into the garden without removing them from the eggshells, be sure to break off the bottom of the shell first. This will free the roots so that they don’t become trapped. The shell will decompose eventually, but not as quickly as the seedling’s roots will grow.
For many houseplants, it’s a good idea to add a layer of small pebbles to the bottom of the pot before adding soil to promote drainage. Or you could just use crunched up eggshells if you don’t feel like buying pebbles for this express purpose. Save up a dozen or so shells, depending on the size of your pot.
Scrub Gunked-Up Tools
Finely-ground eggshells are great for scrubbing gunk off all kinds of things. They’re abrasive enough to get the job done, but not rough enough to scratch metal surfaces. I sometimes use them to scour particularly nasty cast iron pans, but you might do the same with trowels or trimmers.