Your garbage just might be your garden’s treasure. Here’s what you need to know about using eggshells to help your plants grow.
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You might want to think twice before you throw out those breakfast scraps! There’s a much smarter way to use unwanted food items to reduce waste and live more sustainably—and give your garden a boost. Coffee grounds can work wonders on everything from blueberries to hydrangeas, and you might have heard similar rumblings about eggshells for plants. But are they really a good addition to your compost, and how does the science behind this work?
We spoke to Frank McDonough, a former botanical information consultant at the Arboretum of Los Angeles, and Sonia Uyterhoeven, head of horticulture at Greenwood Gardens in New Jersey, to find out whether using eggshells in the garden is a good idea. Ahead, the experts explain the science and how to use it to your garden’s advantage, along with what these discarded bits can do to revive your indoor plants and veggie patch.
After reading the expert’s tips for using eggshells for soil enrichment, you might never toss an eggshell again. Better yet, you’ll witness a change in the health of the plants in your home garden.
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Are eggshells good for plants?
In a word, yes! Eggshells are a great addition to the soil of most gardens and houseplants since they contain calcium carbonate, which strengthens the structure of plants. In fact, all eggs—whether they’re speckled, brown or white—are primarily made of this nutrient and contain potassium and phosphorous. Using eggshells for plants is a great hack that could work wonders for your garden, while making good use of kitchen waste too.
For using eggshells in the garden, McDonough recommends crushing them and adding them to any plants or garden where homegrown compost is used as fertilizer. “There’s no downside,” says McDonough.
He adds that DIY compost without eggshells is often too acidic for a vegetable garden. The high acidity can decrease the plant’s ability to take in nutrients and adversely affect the crop. You can use commercial lime to address this issue, but using spent eggshells fixes the problem for free.
How do eggshells help plants, exactly?
Eggshells’ primary ingredient, calcium carbonate, specifically targets blossom end rot. That’s the deterioration of fruit on certain plants like tomatoes due to calcium deficiency—something that becomes noticeable only when fruits and vegetables start ripening. With tomatoes, for example, water or dark spots might appear on the bottom of the fruit, which will eventually cause it to rot and collapse. This is not correctable after it appears, so you need to take action beforehand.
You can avoid this problem in two ways: regular watering (with the right amount of water to steer clear of dehydration and root rot) and boosting calcium in the soil. That latter solution is where eggshells and eggshell fertilizer come into play.
Eggshells also contain plenty of potassium, just like banana water. The mineral can really benefit your plant’s growth.
What is eggshell fertilizer made from?
Unlike usual fertilizer, which is made from ammonia, DIY eggshell fertilizer contains only one ingredient: eggshells. You have to do a little more than just throw them into your garden—but really, just a little. There are a couple of ways you can go about it.
Small pieces of eggshells
Cleaning, drying and pulverizing the shells will help deliver the best results. That’s because eggshells take a while to break down, so those smaller pieces will deteriorate more quickly and make the nutrients more readily available to your plants.
Powdered eggshells
The Alabama Cooperative Extension found that sprinkling a tablespoon or two of powdered eggshell directly onto a plant’s roots provided the most measurable benefits of adding calcium to soil.
Frozen crushed eggshells
Uyterhoeven prefers crushing eggshells with a rolling pin and adding them to her compost bin. (Worms love it, and eggshells are great for their digestion.) She washes spent shells and adds them to other kitchen scraps in a sealed bin in the freezer. When the container is full, she adds it to her compost.
FYI, putting eggshells in the freezer or drying them in the oven helps them decompose faster.
Store-bought eggshell fertilizer
Wondering if you can buy premade eggshell fertilizer? Commercially produced eggshell fertilizer might be tough to find, but you can try looking for eggshells as an ingredient in store-bought compost. Crushed or powdered eggshells are readily available online, and you can add them to compost or soil, just like shells from your kitchen.
Are there any potential risks of using eggshells for plants?
When we think of using animal products such as eggshells for plants, a common concern is the compost getting infected with bacteria like salmonella. This is especially true for improperly cooked eggs. However, the benefits of using eggshells far outweigh the possibility of them carrying any disease-causing pathogens.
According to Michigan State University, bacteria like salmonella naturally exist in our environment at all times. Eggshells are such a small percentage of your entire compost that they’re rarely able to overwhelm the compost with bacteria. Drying out a batch of eggshells or placing them in an oven can help reduce the risk of contamination. Hot composting at 140 to 160 degrees can also help sterilize the bacteria.
Which plants like eggshells?
While eggshells can benefit a variety of plants, agriculture experts say they’re specifically good for tomatoes, which are particularly susceptible to blossom end rot and could use the extra calcium to combat it. Eggshells also help lower the pH level of the soil and make a more alkaline environment, which many crop-producing plants prefer.
Which plants should you target when using eggshells in the garden? Here are a few:
- Eggplant
- Peppers
- Broccoli
- Cauliflower
- Leafy greens
But don’t go overboard. Since it takes a while for the shells to decompose, Uyterhoeven recommends using eggshells for plants just twice a year—in the fall and spring.
What plants don’t like eggshells?
Don’t add eggshells for plants that prefer acidic soil, like blueberries. Ericaceous plants such as mountain laurel, pieris and azaleas also fall into that category. In extreme cases, low acidity could impact plants’ overall health and/or the resulting crop.
If you’re really not sure what your plant needs, consider getting a soil test to check its acidity or alkalinity. Professional labs, university agricultural departments and local extensions offer the most accurate results since they analyze your sample in a lab.
But honestly, don’t worry too much. Horticulturists say it would take a significant amount of eggshells to really impact the acid level of soil. In most cases, you can safely use eggshells for soil enrichment without worrying. Your best bet, however, will always be with a well-balanced compost; this will be safe for nearly all gardens.
How do you use eggshells for plants?
Making eggshell fertilizer is incredibly low-tech and super easy. Here’s what you need to do:
- Rinse the eggshells after use. Removing egg residue reduces the risk of attracting critters.
- Dry the eggshells. Leave them on the counter for a day or two, put them in the freezer overnight (or longer) or bake them on a cookie sheet in a 200-degree oven for about 20 minutes. Each technique makes the shells easier to crumble.
- Crush the eggshells. You can do this with your hands or by placing them in a plastic bag and using a rolling pin to make the pieces as small as possible. A mortar and pestle, food processor or coffee grinder will get the job done as well. (A coffee grinder will get them closer to a powder.)
- Add 1–2 tablespoons of crumbled or powdered eggshell fertilizer to compost or planting holes. Measurements don’t need to be too exact, but avoid a layer of eggshells at the roots. Be mindful of balance and drainage.
- Plant as normal.
- For existing plants or simply to enrich the soil, add eggshell-laced compost to the top of the soil or lightly incorporate eggshell around the base of the plant.
As noted, you can try this on a variety of indoor and outdoor plants—not just your hard-to-kill houseplants.
How can you make eggshell water?
Because of their sturdy nature, eggshells take a while to decompose. And let’s face it: They are not that attractive circling houseplants. If looking at crushed eggshells for plants in the home doesn’t quite jive with your aesthetic, use them to make liquid fertilizer, or “tea.”
When a plant is not thriving or you’re trying to revive a dead plant, the extra nutrition can help. It’s a great fertilizer for container gardens as well.
Follow the steps below to make eggshell water for plants.
- Crumble eggshells into a pot.
- Cover with water and boil.
- Let the mixture cool overnight so the eggshell goodness leaches into the water.
- Strain to remove the shells.
- Water indoor plants as you normally would, paying special attention to nutrient-starved favorites.
- Put the leftover crushed shells in your outdoor garden or compost pile.
Since hydration is so essential, make sure you’re watering your indoor plants enough (but not too much!). For best results, determine a schedule based on the types of plants in your home.
How else can you use eggshells for plants?
As you can see, eggshells make for eggs-cellent garden fertilizer. But their benefits don’t stop there. Here are more ways to put those shells to good use.
Pest control
If you’re looking to get rid of garden pests, eggshells might be your fix. They have a reputation as a slug deterrent. Some gardeners believe the sharp edges of crushed shells have a negative impact on a slug’s life. To give this a whirl, circle the plant with finely crushed shells. At AllAboutSlugs, that hypothesis did not protect lettuce, so you may want to consider alternatives if you have a serious snail problem.
Seed holders
For the young and youthful at heart, here’s a fun project: Use eggshells to start seeds. It’s adorable, affordable and completely organic.
- Wash out the shell halves.
- Punch a small drainage hole in the bottom.
- Fill the shell halfway with potting mix or seed starter, then add a seed and a little water.
- The egg carton makes a perfect holder! When the plant has several leaves and the weather cooperates, plant it outside—eggshell and all. Just make sure to crack the eggshell in several spots so the roots can expand easily.
Extra nutrients for birds and worms
In addition to using eggshells for plants, you can use them to help other living creatures, like birds. Producing eggs full of calcium takes a fair bit of effort. Help out a feathered friend by adding crushed or powdered eggshell to chicken feed for a well-earned nutrient boost. You can also mix eggshells into bird feeders and vermicomposters for the same reason.
FAQs
Do you have to wash the eggshells before using them on your plants?
Yes, it’s a good idea to wash eggshells before using them in compost. That way, you can limit the risk of bacterial contamination.
Uyterhoeven suggests washing spent shells and adding them to other kitchen scraps in a sealed bin in the freezer before crushing them and using them to enrich houseplants. But you can also wash and then air-dry or bake your eggshells to get them ready for use.
When should you use eggshells for plants?
Whenever you think that plants need an additional nutrition boost, or if you see issues like dark spots cropping up on a fruit or vegetable, it could be a sign that your plant needs calcium. That’s when eggshells can come into play!
Even if you use eggshells only twice a year—in the fall and spring—your plants should do just fine. If plants show further signs of decay, however, it’s better to use a well-balanced compost.
Can eggshells be used as a substitute for commercial lime or calcium supplements?
Absolutely. Store-bought or commercial lime or calcium supplements also contain eggshells or calcium carbonate. So go ahead and make use of this kitchen scrap to enrich your plant’s health.
How long does it take for eggshells to break down and release nutrients into the soil?
It takes a while for the shells to decompose. Though they seem fragile, by nature, eggshells are hardy. That means you’ll likey see sprinkled eggshells atop your soil for a while.
If you don’t like the idea of having visible eggshells in your planters, you could crush them into a fine powder and sprinkle it instead. Alternatively, make eggshell water and simply pour the liquid into the soil directly.
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Sources:
- Sonia Uyterhoeven, head of horticulture at Greenwood Gardens in New Jersey
- Frank McDonough, former botanical information consultant at the Arboretum of Los Angeles
- MSU Extension: “Adding egg shells to compost”
- Alabama Cooperative Extension System: “Crushed Eggshells in the Soil”
- Gardens Alive: “Lots of Plants Besides Tomatoes Love Eggshells. Slugs Don’t.”
- All About Slugs: “Eggshell Myth: good idea or all cracked up?”
