How to Use Eggshells in the Garden: Tips and Myths

by Matt Gibson

Wondering about whether to use egg shells in your garden, and how you’d do it? As the planet is shifting to a greener way of living, the spotlight is on ways to recycle our trash, repurpose our waste, and find new ways to utilize those everyday household items that are all too often tossed into the wastebasket without a second thought.

Just one great way each of us can live more sustainably is to recycle and reuse our “trash,” like the eggshells we feature here. This article delves into how you can give the eggshells you have left over from cooking a new purpose in the garden. At the same time, you’ll be decreasing your own contribution to the landfill.

Recycling is not a modern invention. (The concept and practice actually dates back to ninth-century Japan.) Despite recycling’s extensive history, curbside recycling services didn’t become available in the United States until the 1960s. Citizens are now asked to toss paper, plastic, glass, aluminum, and other recyclable materials into their own container, completely separate container from the other household waste, so these items can be recycled and made into new products. Many gardeners are taking the green life one step farther by repurposing kitchen waste (also known as food scraps) to create compost heaps, effectively turning their trash into healthy, nutrient-rich soil. You know what they say about trash and treasure.

As with any subject, you’ll find as much misinformation out there on the Internet about reusing eggshells in the garden as you’ll find truthful information you can use. There are more than a few widespread myths about ways for gardeners to repurpose the shell of a chicken egg they would otherwise throw away.

That’s why we’ve debunked the common myths in this article—to warn you against putting faith in these old wives’ tales and wasting your time putting them into action. Armed with the knowledge of unexpected ways that you can reuse your old eggshells in the garden, and warned against those common myths that have misled folks in the past, after reading this article, you’ll be equipped to choose the most effective way (or ways) to recycle your empty shells in the garden from this day forward.

First Step: How to Collect and Prepare Eggshells to Recycle Them in Your Garden

After cracking open your eggs and plopping them into the skillet, rinse the shells off with cool water, then place the eggshells into an open container (such as a bowl or a jar with no lid) for long enough to let them dry out completely. Contrary to popular belief, as long as you’ve rinsed them off thoroughly (and the eggs were fresh) dry eggshells do not stink or attract insects. Once you have a lot of eggshells in the container pulverize them into smaller pieces. The easiest way to do this is to use a wooden spoon or mallet. Once they are broken into small enough bits, you will be able to fit many more shells into your containers.

True: Eggshells Can Be Reused as Fertilizer for Garden Soil

Eggshells are mainly made up of the calcium carbonate (which is the carbonic salt of calcium), and calcium is an essential nutrient for giving your garden soil what it needs to nourish plant life. That makes eggshells an excellent source of calcium your garden beds are wishing for.

Calcium is a major botanical nutrient that boosts the ability of the plants in your garden to build healthy cell walls. Once you grind up your used eggshells thoroughly and mix them into the soil, they will go to work to increase the soil’s aeration, improve the soil’s drainage, and reduce the soil acidity. Use a mortar and pestle or a blender to crush the shells down into a fine eggshell powder before you till them into the soil.

You can plan on it taking several months for your eggshells to break down into the soil well enough for them to be absorbed by the roots of your plants. Till the eggshells into your garden beds in the fall so that the nutrients they’ve added will be available to the plants you’ll be sowing seeds for or transplanting outside in the spring. And once spring rolls around, add another batch of eggshell fertilizer to the soil in your garden so that those new eggshells will have time to break down and will be ready to provide nutrients they contain for the plants you’ll be sowing in the fall.

To get even more for your time and energy, you may choose to mix the crushed shells with other types of organic matter and combine them with your garden soil in the areas where you plant to put in new plants in the near future. Tomatoes are one of many garden vegetables that will benefit greatly from the added calcium you’ll get from this eggshell treatment.

You can try a nutrient-rich blend of eggshells and used coffee grounds to amend your soil with boosts of both calcium and nitrogen. Amping up the quality of your soil is one of the simplest and most effective ways to ensure success in your garden, and it doesn’t get any easier or more affordable than reusing your eggshells from cooking that would otherwise be destined for the landfill.

False: Eggshells Don’t Make Optimal Seed Starting Containers (However Cute and Pin-Worthy They May Be)

There are a handful of articles and infographics online that suggest whole tomes of ideas for ways you can recycle your leftover eggshells in your home. One of the methods you’ll see listed most frequently is to create your own seed starters out of eggshell halves.

The instructions for this project will tell you to first collect the larger side of each eggshell half, and then carefully make small holes in the bottom of each one to offer some drainage. After that, you are supposed to add soil and seeds to the shells, then simply watch and wait for newly sprouted plants to appear.

Once the sprouts become seedlings that are ready to transplant, you can plant them directly into the soil as-is, eggshells and all, since the shells will decompose in the soil with time and the roots of your growing plants should break through the delicate drainage holes once they grow large enough and strong enough.

It turns out that using eggshells as seed starting containers is not the best way to repurpose your eggshells for several reasons. First, if the seedlings produce several true leaves, they will all need to be transplanted into larger containers before ever being transplanted into the soil that will be their permanent home. Why not start the seedlings in a larger pot to begin with and skip the extra labor?

Another reason to avoid using eggshells as seed starting containers is that the shells can easily trap the roots of slow-growing specimens and keep the plants from growing to their maximum potential size. The drainage hole or holes that were created at the beginning of the project may provide a large enough crack in the shell’s surface to allow the roots of newly sprouted seedlings to break through, but there’s a good chance that the plant’s roots will be unable to break free and remain trapped inside of the shell instead of expanding freely throughout the entire container or establishing themselves securely deep in the soil below.

Because it takes several months for even the most shattered of eggshells to break down completely and give up their nutrients to the soil, you can likely guess that would take even longer for shells that have only been split in half to decompose. That means for the months-long period of decomposition when their nutrients are not yet free for plants to draw out of your garden soil for an extended period, eggshells that have been repurposed as seed starters in the garden don’t offer any real benefits. Long story short: Eggshells do fertilize soil with calcium carbonate eventually, but they may restrict plant roots, and there’s such a long span of time before the calcium is available that other fertilization methods are more worthwhile.

Undecided: It May (or May Not) Be Worth Your While to Toss Eggshells Into the Compost Heap

It’s true that adding your eggshell fragments to your garden’s compost bin will boost the essential nutrients, making them available for plants the next time you use compost in your garden. However, bear in mind that (as we just discussed) that it will take several months for the eggshells to break down fully so they will be able to release the calcium and other nutrients they contain into the soil. This isn’t such a problem when you’re using eggshells in compost, though, as the other ingredients in the compost also will take a few months to break down and reach their full nutrient-rich potential.

It’s true that tossing your eggshells from their collection container straight into the compost heap seems like a low-effort, high-reward strategy for repurposing what would otherwise be just another piece of kitchen trash. However, when it comes to compost, it’s possible to have too much of a good thing. Eggshells are not just a source of calcium and other needed nutrients for your garden soil.

They also contain a high amount of sodium, and when the shells break down as they decompose, the sodium gets released into the compost heap along with the nutrients your plants need. This is because an excess of sodium in your soil can be toxic to your garden’s plants.

To combat this issue, if you’re going to add eggshells to your compost heap, it’s important that you do testing to keep an eye on the sodium level in your compost as well. If you choose to go ahead with this method, you may wish to only add around half of the eggshells you end up with as kitchen waste to the compost heap. You can reserve the other half of your eggshells to put them to use in another way.

Undecided: Eggshells Can Pitch In to Help Keep Out Certain Garden Pests—While Drawing In Others

Though recent studies have debunked the idea that crushed eggshells will deter snails and slugs wherever they’re sprinkled, eggshells may still provide some benefit as a pest repellent. Crushed eggshells are recommended as an excellent deterrent against Japanese beetles. Also, when they’re added to your garden beds, crushed eggshells have been said to actually prevent deer from grazing on the fruits (or veggies) of your garden harvest. While it is no doubt a blessing that deer can’t stand the smell of eggs, it is a curse that rodents love their sulfurous smell. Although you may see the perks of keeping the local deer population out of your garden, you may not enjoy the corresponding results of inviting neighborhood rodents to your garden getaway. However, if your area has lots of deer but doesn’t suffer from a rodent problem, this strategy may be perfect for your garden.

True: Eggshells Are an Excellent Way to Feed the Birds

Your garden’s plants are not the only forms of life in your yard that can benefit from the calcium your kitchen waste eggshells can provide. Your local birds also need calcium to thrive—especially females, which need extra doses of calcium before and after laying their eggs. If you’re going to use your eggshells as bird food, first sterilize the leftover eggshells by leaving them in a cooling oven after you’ve had it warmed up, then crush the dehydrated shells into fine bits and mix them into your favorite bird seed.

True: Eggshells Make an Effective Garden Mulch

Let’s face it, you may never be able to eat enough eggs to make a two-inch layer of eggshell mulch on top of all of your garden beds. That said, crushed eggshells will work as well as any commercial mulch on the market when it comes to deterring weeds. When you crush those eggshells into small pieces and use them to top your garden soil, the papery white color and fine texture serve to create a surprisingly attractive and unique garden bed.

False: Eggshells Won’t Prevent Blossom End Rot

When you’re growing eggplant and/or tomato plants, you will need to provide a calcium-rich soil that easily transfers nutrients to the developing eggplants and tomatoes. Blossom end rot can occur even when there is plenty of available calcium is present in your garden soil. This issue is is usually caused by irregular watering, a problem that obviously cannot be solved by adding eggshells to the soil. The notion that eggshells can prevent blossom end rot is simply not true. For a comprehensive guide to controlling blossom end rot in your garden, instead check out this Gardening Channel feature article on fighting off blossom end rot.

Ways to Reuse Eggshells Outside the Garden

The garden is not the only place where you can put your leftover eggshells from the kitchen to good use. Check out these ideas for the eggshells you have remaining after you’ve used them in the garden with your favorite strategies from above.

1) Age-defying eggshell facial treatment: Pulverize clean, dried eggshells with a mortar and pestle, then mix them with egg whites to create a healing, restorative facemask. Just rub it on your face, let it dry, and rinse with cool water.

2) Household eggshell cleaner: Mix ground eggshells with a little soapy water to create an abrasive, nontoxic household cleaner that will help you tackle dirty dishes without a ton of effort.

3) Natural eggshell drain cleaner: Keep a handful of ground eggshells in your kitchen sink strainer. The jagged broken edges will help trap solids, and as the shells break down and go down the drain, they’ll also help to keep your pipes clean and clear.

4) Eggshell blemish treatment: Soak a crushed clean, dry eggshell in a container of apple cider vinegar for two or three days, then retrieve the shell. Blot the resulting mixture on minor blemishes, rashes, and other skin irritations to relieve itching and soothe irritated skin.

5) Eggshell health booster for dogs: Dry your eggshells in an oven at 250 degrees Fahrenheit for 30 minutes. Then place the dried shells in a Ziploc bag, seal it, and crush the shells with a rolling pin until they have become a fine powder. Add the powder to your dog’s food to give Fido a calcium boost and improve the health of canine bones and teeth. 

Want to learn more about using eggshells in the garden?

Gardening Know How covers Eggshells in the Garden

Gardenista covers 5 Ways to Use Eggshells in the Garden

Garden Myths covers Eggshells: How Not to Use Them in the Garden

Natural Living Ideas covers Eggshell Uses in the Garden

Reader’s Digest covers 9 Unusual Uses of Eggshells