Most of us use eggs in one form or another almost daily, but eggs can do more than just nourish human bodies.
Eggshells contain several minerals that are essential to plant growth and development, including calcium, nitrogen, potassium, phosphorus and magnesium. Using eggshells in potted plants, either as crushed dry shells or as eggshell tea, is especially helpful since container plants don’t have access to naturally occurring minerals in the ground.
In this article, you’ll learn more about why eggshells are such a great way to add nutrients to your soil. We’ll also go over the details of the 2 methods for adding eggshells to your potted plants:
- Crushed dry eggshells
- Eggshell fertilizer tea
Finally, we’ll answer some common questions. Let’s get started!
Why Use Eggshells in Potted Plants?
We’ve already mentioned that eggshells contain various minerals, but let’s take a closer look at which minerals are present and what they can do for your potted plants:
- Calcium: Eggshells are a rich source of calcium. In fact, according to Healthline, almost half of an eggshell’s volume is made up of calcium carbonate! Calcium helps provide support to plant cell walls and membranes, which maintains strong flowering properties and improves water usage within plants.
Eggshells also contain many other critical minerals in trace amounts. Here are a few of the most important ones for plants:
- Nitrogen: Stimulates new growth and healthy green color.
- Phosphorus: Assists with root growth and strength, as well as stimulating blossoms on flowering plants.
- Potassium: Builds protein, helps with fighting off disease and aids in photosynthesis.
- Magnesium: Essential to chlorophyll production and enzyme usage.
While eggshells do provide lots of beneficial nutrients, they’re not present in high enough concentrations to make eggshells the only fertilizer you need. Compost or commercial fertilizers provide balanced nutrition for plants, so you’ll still need to apply these periodically throughout the growing season.
But eggshells make a fantastic additional nutrient source, particularly for calcium, which can be harder to come in standard fertilizer formulas.
Not only is adding eggshells to potted plants a wonderful natural fertilizer, it’s also just a great way to reduce the amount of trash you throw out. And if your eggs come in a paperboard carton and you have a composter, you can have a totally zero-waste food! Which I think is pretty cool.
Sounds pretty great, right? Let’s move on to how you can take advantage of eggshell nutrition for your own plants.
Method 1: Using Crushed Eggshells for Potted Plants
Eggshells take a long time to break down to provide the nutrients listed above if you use them in big chunks. So it’s not as easy as crushing the eggshell in your hands (ouch, by the way!) and tossing it into your potted plants.
According to a study done by the Alabama Cooperative Extension System at Auburn University, you need to crush your eggshells to a fine powder texture to get maximum calcium absorption. In fact, the researchers found that powdered eggshells performed nearly as well as commercial calcium soil amendments!
The study also found that the calcium stayed bound up in the shell material for longer when the shells were crushed to a coarser texture, so less calcium made it into the soil in the short term.
That being said, your plants can still benefit from eggshells even if you don’t grind them down into fine powder. Here’s what slightly larger shell fragments do:
- Better drainage
- Increased soil airflow
- Nitrogen boost for a short time
So whatever size pieces you end up with, they’ll be good news for your plants. Let’s cover the steps of preparing crushed eggshells:
1. Rinse Your Eggshells
Raw eggs are a risk for salmonella and other food-borne illnesses, so rinse the empty shells out well as soon as possible after cracking your egg open.
Also, leaving any residual egg white leaves your eggshell sticky on the inside, which can make them harder to crush up properly later on.
So give your shells a good rinse right away!
2. Dry Your Eggshells
After rinsing, your eggshells need to dry thoroughly.
Many people choose to put their shells into the oven at 250 degrees for about 30 minutes, and some boil the shells for a couple of minutes before oven-drying. These steps kill any salmonella or other microbes that might still be hanging around.
I like to arrange my shells in a single layer (make sure no shells are nested inside each other!) and put them in a sunny window for a few days.
Either way, you’ll know when your shells are totally dry and ready for crushing by looking at the membrane. When it perforates easily with just a light touch from your finger, they’re dry:
3. Crush Your Eggshells
There are a few methods for crushing up your eggshells:
- Food processor
- Coffee grinder
- Mortar and pestle
- Zip-top plastic bag and rolling pin
Keep in mind that different methods are going to produce different sizes of eggshell pieces. A high-speed blender, food processor or coffee grinder will produce the finest particles, which is ideal if you’re trying to address a specific calcium deficiency in your soil.
The manual methods (mortar/pestle, plastic bag/rolling pin) will also produce some powder but will have mostly coarse pieces. This should be perfectly fine for routine soil texture improvement and enrichment.
SAFETY NOTE: If you’re planning to crush your shells in a blender, food processor, coffee grinder or mortar/pestle that you also use for food, you need to take the extra time to boil and oven-dry your shells. It’s not worth the risk of illness to just save a few minutes. Also, be sure to wear a mask or cover your face so you’re not breathing in the dust from the eggshells.
I like to do things the non-electrical way whenever I get the chance, so I’m using the rolling pin/plastic bag and mortar/pestle methods here. Since I dry my shells in the sun, I use a mortar and pestle that I dedicate to crushing eggshells only.
Here are the shells of about seven eggs in a zip-top bag and what I ended up with after going over them with a rolling pin several times:
And here are the results from the shells of about five eggs in the mortar and pestle:
Let me tell you- you’ll get an arm workout when you do either of these! But they get the job done.
4. Adding Crushed Eggshells to Potted Plants
Once you’ve got your eggshells crushed to a point you’re happy with, you’ve got a couple of ways you can use them.
For plants that are already established in their pots, pour a thin layer of your crushed shells on the soil surface around the base of your plant, then water your plant well. The water carries some of the eggshell fragments down into the soil, feeding your plant’s roots at the same time. And each time you water, a little more gets carried down.
Here are some I put in my pothos pot:
If you’d like to, you can lightly scratch the crushed shells into the soil right after application, but it’s not totally necessary. The water will do most of the work!
For plants that you’re potting for the first time or are repotting, you’ve got a couple of things you can do:
- Mix a handful of crushed eggshells into your fresh potting soil.
- Add a layer of crushed shells to the fresh soil right underneath where you’ll place the root ball.
Again, water well after you finish the potting process to help your shells incorporate into the soil.
Method 2: Using Eggshell Tea in Potted Plants
Preparing crushed eggshells is pretty easy, but this one is even easier!
1. Rinse Your Eggshells and Set Out to Dry
You need at least 10 eggshells to make a batch of tea, so you’ll probably have to save up for at least a couple of days.
Just like we talked about earlier, rinsing your eggshells washes away potentially harmful raw egg liquid. Give your shells a good rinse and lay them out in a single layer in a sunny spot or outside.
But if you’re making an egg casserole some other egg-heavy dish that yields 10+ eggshells at a time, rinse your shells and move right on to step 2.
NOTE: If you want, you can do the oven-drying step we talked about earlier right now, too. But you’ll be plunging your shells into boiling water in the next step, so the risk of salmonella or other microbes is less than with crushed shells. However, oven-drying doesn’t hurt anything, so it’s up to you!
2. Make Your Eggshell Tea
Fill a pot with 1 gallon of water and bring it to a full boil. Remove from the heat and add between 10 and 20 eggshells.
Allow it to steep at least 12 hours, then run your tea through a strainer to remove the eggshells. Don’t worry about using a fine-mesh strainer or anything; these are pretty big shell pieces so a standard colander is totally fine.
3. Water Your Plants with Eggshell Tea
This step is pretty self-explanatory. According to the University of Illinois Extension, 2 cups of tea per potted plant is the ideal amount for plants in large pots, like tomatoes in a 5-gallon bucket.
But obviously, for houseplants or outside plants in small pots, 2 cups of water will likely over-saturate the soil. So just use the normal amount that you would in a standard watering.
Repeat weekly with fresh tea, or however often you have enough shells to brew another batch.
Also, when you boil eggs, don’t let that water go to waste- it will make a weak tea of its own. Let the water cool when your eggs are hardboiled, then use it to water your plants in the same way we talked about above.
Which Method for Using Eggshells in Potted Plants is Best?
Both methods for using eggshells in potted plants are good, and your plants will benefit from whichever one you choose.
But here are a couple of tips for deciding which one is best for you:
- If you’re trying to seriously bump up the calcium levels in your soil, powdered dry eggshells are definitely the way to go.
- If you’re wanting to provide better drainage, aeration and a smaller nutrient boost over time, coarsely crushed shells are ideal.
- If you’re already happy with your soil structure, want a weaker fertilizer for routine use or you just don’t want to deal with the crushing process, eggshell tea is the perfect option.
Which Plants Are Eggshells Good For?
Container gardening is on the rise, and many container-friendly plants appreciate the soil enrichment eggshells provide.
In particular, veggies in the nightshade family (tomatoes, eggplants and peppers) will benefit from the high calcium in eggshells.
This family of plants is prone to blossom end rot, which is where the fruit starts to go rotten early in the season before it’s even ripe. Blossom end rot is often due to a lack of calcium in the soil, so enriching the soil is a great way to avoid this disappointing problem.
But nightshades aren’t the only veggies that love eggshells. Here are some more:
- Swiss chard
Several (non-vegetable) plants also benefit from eggshells:
- Houseplants, like philodendrons and pothos
- Butterfly bush
These lists are by no means exhaustive, and almost any plant can benefit from the nutrients that eggshells have to offer.
Although we’re talking specifically about adding eggshells to potted plants here, the truth is that plants growing in the ground will also appreciate the calcium boost that crushed eggshells or eggshell tea provide.
So whether it’s for houseplants, a container garden or an in-ground garden, start saving those eggshells!
When to Be Careful with Eggshells in Potted Plants
Remember when we mentioned earlier that powdered eggshells were nearly as potent as commercial agricultural calcium? This can be either good or bad.
There is such a thing as calcium toxicity, or calcium levels that are too high. According to the University of Missouri, when there’s too much calcium, it can interfere with the action of other critical minerals, namely magnesium and boron.
You’ll likely only run into this problem if you use eggshells ground to a fine powder since coarser eggshells and eggshell tea don’t release nearly as much calcium. So limit your powdered eggshell application to once a year, unless a soil test reveals a significant calcium deficiency.
Also, don’t use eggshells around plants that love highly acidic soil, with azaleas and rhododendrons being the most common. Eggshells are alkaline in nature, so they could alter the soil pH balance enough to affect these plants’ color or production.
Frequently Asked Questions about Eggshells in Potted Plants
Adding eggshells to potted plants shouldn’t be the sole source of fertilizer you use, but it’s a great addition to your fertilizer routine. Not only can you prevent adding to landfills, you can improve your soil’s texture, help your plants grow healthy and strong and potentially ward off pests.
What’s not to love?