Why Do People Put Eggshells on Plants?

Some people swear by the old trick of putting crushed or tiny eggshell pieces in the soil to help plants grow. If you google “eggshells on plants,” the top results will tell you that eggshells are full of minerals like calcium, potassium, and phosphorus that are all beneficial to plants when broken down and absorbed. 

There are naysayers, though, who believe soil for growing plants is likely already rich in calcium, and that the benefits of crushed eggshells are overstated. Plus, eggshells take a long time to break down anyway (unless you maybe toss them into the blender before sprinkling the bits into the soil).

But then there is the phenomenon of eggshells being placed on leaves or on the actual plant (versus mixing them into the ground). Apparently, it’s a common practice for many gardening enthusiasts, here and elsewhere in the world, particularly for plants with pointy leaves, and even orchids.

But why exactly is it done?

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Eggshells on plants

A casual internet search will yield multiple guesses but no definitive answer. On Reddit, there have been a couple of threads over the years devoted to this very topic.

When you ask Redditors, the most popular answer seems to be that eggshells are left on plant leaves so they can dry under the sun before they’re crushed and thrown into the ground.

“I think pinapatuyo muna kaya naka-’sampay’ siya sa halaman, saka siya dudurugin and ihahalo sa lupa,” said u/ yo0gen3.

“Dati kala ko for decor purposes lang haha pero ginagawa yan ng nanay nung lumipat kami sa province to dry the shells,” said u/mandemango. “Kapag dry na saka dudurugin at gagawing pataba.”

Somebody even theorized that the eggshells are placed on plant leaves as a kind of “slow release tactic.”

“Eggshells are made up of calcium carbonate which is soluble to water,” said u/ SAHD292929. “Now if nasa taas ng dahon at sa bawat dilig sa dahon, mag trickle down ito sa lupa ng mas mabagal at hindi ma shock ang tanim sa sudden change of pH ng lupa sa paso.” 

Interestingly, somebody commented that former Department of Health Secretary Juan Flavier himself said something about this practice.

“This is so old Flavier talked about it on one of his books as a doctor to the barrios,” said u/ cocoy0. “So despite the usual explanation about fertilizing plants, he jokes about it as rural people putting eggshells on plants to let neighbors know they are so well-off they can afford to cook eggs instead of selling them.”

And it’s true that eggshells-on-plants is far from being a recent phenomenon. u/nickaubain posted a new thread about the same issue in April 2022 with a photo purportedly taken in the early 1900s by Dean Conant Worcester. The black-and-white photo shows what appears to be a type of snake plant with eggshells attached to the top like tiny umbrellas. 

“I'm going to say it's either ornament(al) or cultural because we've been doing this for hundreds of years at least,” u/nickaubain says.

Eggshells ON plants
by u/nickaubain in Philippines

In this new thread, people seem to also think that the eggshells serve a safety purpose.

“It's mainly for aesthetics of spiky plants but also for the safety of children,” said u/ramosgerald255. “Here in the province, it's common to see kids running around your garden. You don't want them to cause extra hassle if they poke their eyes into your spiky plants, so they do this.”

“My mom does this kasi matulis yung dulo ng halaman kaya ginagawang pantakip para di matusok (kahit nadadali parin ako XD) added na rin siguro na madudurog yung egg shells eventually sa lupa pag naluma and maging fertilizer,” agrees u/ Otherwise-Selection3.

And one user actually said he asked “old people” for their take on the whole thing.

“Some of the answers I got from old people I asked,” wrote u/SantySinner:

“1| So the tips won't dry up. (Idk, but I do observe that the tips gets dried up but still doesn't make sense cuz if that's so, then the whole leaf should also dry up.)

2| To avoid getting poked in the eye.

3| "Hindi ko alam, nakita ko lang", lolo is so real for this.

4| Fertilizer(?).

5| ‘Palamuti lang’

6| Bugs won't eat it daw.”

What is the truth?

Putting eggshells on plants is apparently one of those things people do that have no basis in fact other than anecdotal evidence. One person sees another person doing it and make automatic assumptions.

We can’t find a definite answer to the hypothesis that eggshells add calcium to the soil, and therefore is good for plants. What we did find is an exhaustive study to find out whether eggshells decompose in the first place and release said nutrients into the ground.

According to GardenMyths.com, eggshells don’t dissolve in water, and takes a very, very long time to decompose in soil. The person who runs the site said they conducted a five-year study to determine whether eggshells would break down in soil within five years. The answer, it appears, is no. Unless you grind them up into very, very small particles (like in a blender or grinder), eggshells can last for a very long time. In fact, after five years, the eggshells he put into the ground “don’t look any different than after one year.” 

“Eggshells are extremely stable and don’t break down very fast without some help,” the site said. “Water alone does not seem to break down the eggshells. Acidic soil will break them down, but only if the soil is acidic enough and if the eggshells are very finely powdered. Most gardeners don’t powder the eggshells before putting them into the compost bin or spreading them in the garden.”

Of course, this study is not peer reviewed and has not been published in a reputable science journal or publication. It’s just another thing we found on the internet. But it seems to offer the most solid and reputable evidence of what exactly happens to eggshells buried in the ground.

“It is my belief that eggshells simply break up into smaller and smaller pieces while people work the soil, until you don’t see them,” GardenMyths said. “You think they are decomposed, but they are still there in small pieces. Pieces that are much larger than finely ground.”