Does putting eggshells in your garden really help your plants grow? Will the calcium in the eggshells give your plants an extra boost? Let’s see what the experts and the scientific research have to say.
There is a lot of advice for gardeners that is either exagerated, misleading, or one of many garden myths, and we all fall for them at some point!
Should We Add Eggshells to the Garden?
Gardeners sure love to add eggshells to their gardens and all sorts of claims are made about their effects on plants. But, as you’ll see, much of this is anecdotal, and while they really won’t do harm, they just don’t have the superpowers we wish they did.
- Do Eggshells Really Give Plants a Boost?
- Calcium and Blossom End Rot
- Eggshells In the Compost Bin
Do Eggshells Really Give Plants a Boost?
So, are eggshells good for your garden?
Plenty of people think so, but the short answer is, no: not for short-term plant boosting.
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.
Related: Is Vinegar a Good Weed Killer?
And, even if extra calcium would help, eggshells aren’t the best way to do it.
Unless you grind them to a very fine powder, they’re just going to sit in your soil as broken eggshells for years until they decompose. And even if you do grind them into powder, there is little or no value.
Either way, they will eventually decompose, so maybe they’ll help your garden many years from now—again, only if your soil is calcium deficient—which it probably won’t be—but this is all contradictory to the common advice we hear in garden forums.
That said, the eggshells aren’t going to do any harm, can contribute to soil structure, and composting them is better than sending food waste to landfill, but just don’t expect to see any improvements in your garden because of them.
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 anecdotal at best.
Calcium and Blossom End Rot
You will sometimes hear it said that adding eggshells will prevent what’s known as blossom end rot (BER), a problem that shows up during some tomato growing seasons.
After checking the research it seems that what causes BER is not entirely understood.
This condition does relate to calcium uptake and moisture stress (uneven watering) but is usually not caused by calcium deficiency in the soil.
More commonly, the problem is that the plant isn’t absorbing the calcium that is in the soil, and adding eggshells isn’t going to address that problem.
In other words, it may be a calcium uptake problem, not a calcium deficiency issue.
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
Eggshells In the Compost Bin
So, it may sound good, but no matter how many times you’ve heard this one, and will continue to hear it, the best evidence we have says that adding eggshells is not going to provide any immediate benefit to your garden.
Or, at least not any of the benefits that popular gardening advice claims they do.
The will add some calcium at some point—gradually, after many years—but most of our gardens are not calcium deficient so it’s not really essential.
But, composting avoids sending things to landfill, and that’s good.
Mash up your eggshells prior to composting to avoid waiting years for those shells to crumble and continue adding a good variety of greens and browns to your bin.
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 indicated 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.
See Popular Garden Myths We’ve All Fallen For for other popular myths and misinformation.
Garden Soil 101
Soil | The foundation of your garden. Know what you’ve got and provide only what it needs.
• Mulch | Add 2-inches of organic matter to protect soil, retain moisture, and gradually fertilize your soil.
• Leaves | Finely chopped fall leaves make excellent mulch.
• 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.
~Melissa the Empress of Dirt ♛