Using Eggshells in the Garden: 7 Mistakes to Avoid

Eggshells have some great uses in the garden, but there may be some misconceptions out there about how and when they are useful. Join gardening expert Melissa Strauss to discuss some mistakes that you can avoid when using eggshells in your flower beds.

Written by Melissa Strauss Horticulture review by Sarah Jay Last updated: May 12, 2025 | 5 min read

A female gardener applies crushed eggshells to garden beds with fresh lettuce plants in a sunny garden.

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When it comes to using eggshells in the garden, there are some excellent ways that they can contribute to the health of our plants. They are useful as a natural fertilizer, contributing nutrients that fortify the soil. They deter pests with their sharp edges, and they can help aerate the soil as well.

If you use them properly, the container that your eggs come in will contribute great things to growing plants. For those that prefer a neutral to alkaline environment, they raise the pH of your soil, making it a more hospitable place for specific inhabitants.

If you use them correctly, they can improve the structure of your soil, add calcium, deter pests, and give a slight boost of other valuable nutrients. That said, they are not a fix-all for gardening issues. There are right and wrong ways to add them to your routine. Here are some mistakes that you can avoid so that you can make effective use of eggshells in your garden.

Not Prepping Them First

Female hands wash brown chicken eggs under running water from a kitchen tap. — Clean first—no one wants surprise bacteria near the tomatoes.

Eggshells are useful in the garden, but you’ll lose many of the benefits if you don’t prep them properly. Like most things in life, there is some work involved in the process if you want to reap the benefits.

The most important thing to do is to wash them. I will say that this is most important if you’re getting your eggs from a backyard flock, and unwashed. I have backyard chickens, so I don’t wash my eggs until I use them. Even then, there is a slight chance that your shells could house pathogens that you don’t want around your vegetables.

Not Crushing Them Enough

A woman's hand holds a handful of crushed eggshells against a blurred background of a basket full of uncrushed eggshells. — Finer bits mean faster benefits for your soil.

You’ll also want to dry and crush them. Large chunks won’t break down and be as beneficial. It’s good to let them dry thoroughly first, so they are easier to crush. Some folks toss their shells on a baking sheet and put them in a warm oven to dry them out. Then, crush them into fine pieces before using them on your plants.

If you’re using them for pest control, to ward off soft-bodied insects, leave them a little coarser. You want it to be uncomfortable for snails and slugs to move through them. However, if you’re using them as fertilizer, the finer you grind them up, the better. This way, they will break down faster for your plants to use.

Using Them With Acid-Loving Plants

A female gardener wearing black gloves applies crushed eggshells as fertilizer to young cucumber plants growing on a wooden raised bed in a sunny garden. — Not everything in the garden enjoys a calcium kick.

Eggshells have an alkalinizing effect on the garden, raising the pH of the soil they break down in. Calcium carbonate is their primary mineral, and you might recognize this from that bottle of antacids in your pantry. It’s used as an antacid to neutralize your stomach acid. They have a similar effect on soil.

Now, this can be both positive and negative. Some plants appreciate a more neutral to alkaline pH. Many herbs, brassicas, beans, and others benefit from bringing down the acidity. They’re great for adding to the soil around these plants.

Conversely, there are plenty of plants that prefer acidic soil, and giving them eggshells will have a negative impact. Many types of berries, rhododendrons, magnolias, dogwoods, peppers, and sweet potatoes won’t get the nutrients they need from alkaline soil.

It’s always good to run a soil test before you make amendments. Identify which plants in your garden prefer acidic, alkaline, or neutral soil. If your soil leans in the neutral or alkaline direction, avoid adding them around acid lovers.

Starting Seeds in the Shell

Young pepper seedlings with thin upright stems and oval leaves grow in eggshells filled with soil on a wooden table in the garden. — Whole shells take too long to benefit young plants.

I’ve seen some recommendations about starting seeds in your eggshells, claiming that this helps with nutrients and repurposing them. I have to be a naysayer on this one, as they don’t release nutrients into the soil until they decompose. Whole shells won’t do that in the time it takes for your seedlings to outgrow them.

That brings me to my next point. An eggshell has a small cavity, and most seedlings will outgrow it quickly. This means smaller seedlings that you’ll either have to repot or put in the ground while they are weak and spindly.

There are arguments for planting the seed in the shell, directly into the ground. The idea is that the eggshell will decompose naturally and feed the plant. It’s a nice thought, but those whole shells will take a long time to decompose and will inhibit root growth.

Expecting Immediate Results

Young radish seedlings are fertilized with crushed eggshells on top of black loose soil. — It breaks down slowly, but pays off in the long run.

While it is true that eggshells will break down and enrich your soil, it won’t happen overnight. In fact, it’s unlikely to be helpful at all to your current vegetable patch. They will add to the soil over time, though.

The issue is that, again, it takes quite a long time for the shells to decompose. They will sit in the soil for months to years, depending on their degree of processing, before they do any good. Once they break down, they add calcium, as well as small amounts of magnesium, potassium, and phosphorus. They also improve the soil structure if the particles are coarser.

If you process them properly, wash, dry, and thoroughly crush them, you will reap the benefits in a few months. Whole shells or large chunks can take years to break down and contribute. Adding them to your garden is a long game; it will benefit your plants down the road, but you shouldn’t use them as a substitute for other fertilizers.

Using Them to Prevent Blossom End Rot

Close-up of a gardener's hand in a grey glove applying crushed pieces of shell to a young pepper plant with shiny, oval leaves with tapering tips on a tall stem. — There are no quick fixes—rot prevention starts with solid soil prep.

Blossom end rot is a real pain for anyone who grows tomatoes. It can also show up in peppers, melons, squash, and eggplants. It’s the result of a nutritional deficiency, along with insufficient watering. Tomato plants need a lot of water.

This issue is indeed linked to calcium deficiency, and over time, adding eggshells to your soil can help. Often, when plants aren’t taking in the calcium that is in the soil, it’s because of acidity. These crops need soil with a pH that is close to neutral. If the soil is too acidic, it won’t break down the calcium in a usable way.

Adding shells over time, and I mean a lot of time, years, will make things more alkaline, and also contribute some additional calcium. It just won’t be useful this season. Adding them directly to the holes where you plant your tomatoes won’t do much at all for this generation of tomatoes.

If your soil test shows up with low calcium or an overly acidic pH, lime is a better treatment. It works faster, raising the pH in time to benefit the things in your garden this year.

Overestimating Them as a Calcium Supplement

Young seedlings with green leaves grow in a raised bed fertilized with eggshells. — A few shells won’t tackle a calcium deficiency quickly.

If you have a legitimate calcium deficiency in your garden, eggshells aren’t likely to improve that problem in the short term. At least, not in the small amounts that most of us have on hand. Just like the other nutrients, it takes the calcium they contain a year or longer to break down and become beneficial to your vegetables.

One eggshell contains about four milligrams of calcium. That’s not much. If you have a great deal of them at your disposal, they may help with a deficiency. However, a few dozen a season isn’t likely to make a dent.

In any case, if you want to use them for this purpose, it won’t do any harm, as long as your soil pH is slightly acidic. It just won’t have the intended effect immediately. They are not a substitute for other forms of nutrients, including calcium. The finer you crush them, the faster they will break down.