Last fall, I started collecting eggshells after I read an article on Realfarmacy.com that touted their usefulness in the garden, for everything from fertilizer to organic pest control. This spring, I’m using crushed eggshells in the garden five ways:
Photography by Justine Hand for Gardenista.
Above: During the winter, I saved the shells from all the eggs we ate by simply rinsing them and placing them in an open container where they could dry out. (No, they did not smell. Everyone who came to my house and saw them asked me this question.) After my containers were full, I set the kids to pulverizing them into little bits with wooden spoons, thus compacting the shells so that I could collect more.
Above: When tilled into the soil, ground eggshells provide your plants with calcium.
Though nitrogen, phosphorus, and potassium are most vital for healthy growth, calcium is also essential for building healthy “bones”—the cell walls of a plant. Composed of calcium carbonate, eggshells are an excellent way to introduce this mineral into the soil. To prep the eggshells, grind with a mixer, grinder, or mortar and pestle and till them into the soil. Because it takes several months for eggshells to break down and be absorbed by a plant’s roots, it is recommended that they be tilled into the soil in fall. More shells can be mixed into your soil in the spring.
By the same token, finely crushed shells mixed with other organic matter at the bottom of a hole will help newly planted plants thrive. (Tomatoes especially love calcium.) For an exciting recycled garden cocktail: try mixing your eggshells with coffee grounds, which are rich in nitrogen.
Finally, eggshells will reduce the acidity of your soil, and will help to aerate it.
Eggshell Seed Starters
Above: Because they are biodegradable, eggshells make excellent, no-waste seed starters. For this, reserve some of your deeper shell halves. Sterilize the shelves by boiling them or by placing them in a 200 degree oven for 30 minutes. (If you put them in a cooling oven after, say, you baked a roast chicken, you can sterilize eggs without using excess energy.)
Next, with a nail or awl, make a hole in the bottom for drainage. Add soil and seeds according to the packaging. When sprouts appear, plant them—egg and all—right into the soil. See a complete DIY at 17 Apart.
Eggshell Pest Control
Above: A coating of crushed eggshells in the garden is said to help deter several pests, both large and small. Deer dislike the smell of the albumen and will stay away. Apparently you can also use egg’s insides to deter deer. See DIY: Homemade Deer Spray. Be aware, however, that though deer hate the smell of eggs, rodents love it. Therefore, it may not be best to use this deterrent near the house.
Many gardeners also tout the use of crushed eggshells as a snail and slug repellent. But a recent test by All About Slugs in Oregon seems to have dispelled this as a myth. If you’ve had any success with egg shells as slug repellent, we’d be curious to know.
Eggshell Bird Food
Above: Like plants and people, birds also benefit from a bit a calcium in their diet, especially the females who need extra before and after laying their eggs. To make bird food, start by sterilizing the shells by leaving them in a cooling oven after you bake a meal. Then crush them into fine bits and mix with your favorite seed.
Above: Like oysters (See A Gift from the Sea: Oysters in the Garden), eggshells used as mulch provide a striking accent in the garden. If you gather enough, you can even apply a layer thick enough to deter weeds.
Looking for more recycled garden how-tos? See:
- Dirty Secret: 10 Ways to Improve Garden Soil.
- Seafood for the Garden: Make Your Own Organic Fertilizer.
- Gardening 101: How to Use Fallen Leaves.
- How to Sprout Seeds and Grow a Compost Garden.