Are eggshells good for plant growth? A beneficial source of calcium? Can they deter slugs? Let’s look at what’s known about eggshells as a fertilizer and pest deterrent in the garden.
A lot of popular garden advice falls under the category of garden myths. Many tips sounds good but contradict what science knows about how plants grow.
Garden Myths About Eggshells
Gardeners sure love to add eggshells to their gardens and make all sorts of enticing claims about their benefits. But, as you’ll see, much of this is anecdotal or exaggerated and, while they really won’t do harm, they just don’t have the superpowers we wish they did.
- Are Eggshells Good For The Garden?
- Blossom End Rot
- Composting Eggshells
- Do Eggshells Deter Slugs or Snails?
Eggshells & Gardening
Contrary to popular belief, eggshells are not unusually beneficial for growing plants. There is a common misconception that because eggshells have calcium, our soil and plants must need it. However, garden soil is rarely calcium-deficient.
If there is a calcium deficiency in plants, it usually indicates an uptake problem—not a need for more calcium in the soil.
On the plus side, eggshells do contribute to soil structure and, over a long time, gradually release some micronutrients as they decompose.
There is no harm in adding eggshells to a garden. Added to a compost pile, eggshells will gradually decompose along with other organic matter. They will break down faster if chopped up or grinded into a powder first.
It’s easy to understand why this gardening myth refuses to die.
Eggshells are calcium!
Calcium’s good for you! Builds strong bones!
So, let’s put it in the garden!
And, it’s not entirely a myth. Your plants do need calcium and eggshells provide it—that part’s true!
But, there’s probably plenty of calcium in your soil already, so adding more calcium isn’t going to change anything.
And, even if extra calcium would help, eggshells aren’t the best way to do it.
The good news is, eggshells aren’t going to do any harm, can contribute to soil structure, and composting them is better than sending food waste to landfill. Just don’t expect any noticeable improvements by adding them to your garden.
If anyone tells you their plants changed quickly after adding eggshells to the soil, it’s a classic case of confusing correlation with cause and the claims are anecdotal at best. Light, air, soil quality, water, and the plants themselves all play a role in plant health.
Related: Is Vinegar a Good Weed Killer?
Blossom End Rot
No, adding eggshells to soil will not prevent or resolve blossom end rot (BER). And, once the rot has occurred, the fruit will not heal. While not entirely understood, BER seems to be an issue with calcium uptake and moisture stress in plants like tomatoes, not a calcium deficiency. Low soil pH levels and over-fertilizing may also play a role.
The popular advice to add tums or eggshells to solve the problem is a myth.
If the problem persists, this is where a good soil test from an accredited lab can provide a complete analysis and any recommendations.
But, most often, BER is a one-time issue and the next growing season will be fine.
Related: Soil Testing: Home Kits versus Lab
Composting food scraps like eggshells is better than sending them to landfill sites.
While not necessary, you can chop up or grind eggshells into small pieces or powder to help speed up decomposition.
There is no need to bake eggshells prior to composting. Some gardeners feel this is required to remove pathogens but there is no evidence this is necessary.
Deterring Slugs & Snails
The idea that crushed eggshells will deter slugs or snails is a myth. These animals have a slime-like mucous on their bodies that protects them from sharp surfaces including eggshells.
Slugs and snails do not avoid sharp surfaces—they just take the easiest route from A to B.
The idea of using a barrier of crushed up egg shells around a plant to keep slugs away is neither proven nor practical.
The slimey mucous along with extremely tough skin both protects them from hazards like this and also assists with their mobility. Eggshells be darned!
This video shows how they behave when surrounded by crushed eggshells.
After watching, be sure to check out these tips for dealing with slugs and snails.
Garden forums are filled with testimonies claiming that adding eggshells (and sometimes whole eggs) gives a same-season boost to plants.
Here’s what we know:
- The popular advice to improve plant health with eggshells is misleading (modern garden folklore).
- The idea that calcium is deficient in soil, that eggshells instantly provide it, and plants take it up and flourish are all problematic.
Soil tests rarely indicate calcium deficiency. If a plant is truly calcium deficient, it is often an uptake problem—meaning it is unable to use the available calcium, which is not solved by adding more. Plants cannot overeat.
- Eggshells are just one of many organic foods we can compost, contributing micronutrients and structure, taking many years to break down.
Eggshells are fine to include in compost (like many other things) but not a magical superfood.
- Correlation is not cause: just because you added eggshells and plants did well does not mean that was the cause. Light, air, soil quality, water, and the plants themselves all play a role in plant health.
- A hungry snail is not going to let some crushed eggshells deter him from getting to a food source.
- See Popular Garden Myths We’ve All Fallen for other popular myths and misinformation.
- Beginner’s Guide to Organic Fertilizers
- Answers to Frequently Asked Tomato Questions
- Dealing With Slugs & Snails Without Harming Your Garden
Garden Soil Tips
Soil | The upper layer of earth in which plants grow, a black or dark brown material typically consisting of a mixture of organic remains, clay, and rock particles.
Mulch | Placed on soil, organic mulch can protect soil, retain moisture, and gradually fertilize the garden.
Leaves | Finely chopped fall leaves make excellent mulch.
Leaf Mold | Decomposed fall leaves beneficial to soil structure.
Compost | Decomposed organic matter providing nutrients for the garden.
Potting Mix | Contains no soil: designed to optimize plant growth in pots.
Seed Starting Mix | A lightweight potting mix for sowing seeds in containers.
Soil pH | Knowing your level (which may vary) is informational, not a call to action. Most soils fall in the range of 5 to 8 and accommodate a wide range of plants.
Free Soil Calculator Tool | Estimate how much you need and what it will cost
~Melissa the Empress of Dirt ♛
Empress of Dirt
Reader’s favorite tips and tutorials on various topics compiled into handy downloadable ebooks.