Even the most green-fingered of us is going to have times where our plants look a little sickly. I know I do.
Unfortunately it’s not always easy to diagnose the problem – nutrients, water, light, heat, disease, etc etc. So wouldn’t it be great to have something cheap (or even better, free) you could try to pick them up?
Well it turns out there is, indoor gardening friends. The not-so-humble egg shell. I only found this out recently, but you can use egg shells to make a really nourishing fertiliser for your plants.
Most of us throw shells out without a second thought once we’ve enjoyed the contents. But hopefully I can persuade you to start saving them, because they’re crushable little powerhouses of essential plant nutrients.
Why egg shells are great for indoor plants
Unlike outdoor plants, plants grown in pots indoors can’t send roots deep into soil to seek out minerals. So supplementing them with extra nutrients can help to prevent any deficiencies.
Which is where those shells come in…
Egg shells are incredibly rich in calcium. They’re composed of about 95% calcium carbonate – the same stuff our bones and teeth are made from.
Though perhaps not the tastiest snack, egg shells are actually edible.
So if you fancy a crunch, half a shell will provide your daily recommended intake of calcium!
Calcium – why it’s needed for plant health
Just like us, plants need a balanced diet of nutrients to stay healthy. Nitrogen, potassium and phosphorus are the most important for plants, and considered the primary nutrients.
But smaller amounts of secondary nutrients are vital to keep plants in optimal health too. Calcium is one of them, along with magnesium and sulphur (both also found in small amounts in egg shells).
Along with enzyme activity and metabolism, calcium is essential for helping plants build strong cell walls. A lack of it can leave plant cells weakened and vulnerable to pathogens. And this in turn can lead to all manner of nasty ailments.
Leaf edge necrosis, leaf curl, tip burn, root disease, stunted or deformed growth, blossom end rot – all can be caused by calcium deficiency.
So feeding your plants with calcium-rich egg shells can keep them fighting fit, help to stave off those nasties and encourage healthy growth.
How do you make egg shell fertiliser?
There’s a choice of ways you can use egg shells to feed your plants, so you can experiment and see which way works best.
It won’t cost you a penny after all, so you’ve nothing to lose. Just remember to keep a note of your results so you know which way was most effective for future reference.
The simplest way to make your plant feed is to crush the shells into a fine powder and apply or mix them into soil.
But you can also use egg shells to make a liquid fertiliser, using either water or vinegar as the base. The vinegar way is slightly more involved than water – but really not much.
In fact, all the methods are pretty simple.
Using powdered egg shells in potted plants
To make the powdered feed, first you’ll want to give the shells a good wash inside with warm water.
There’ll be protein residues in there which may get a little whiffy in time, as well as encouraging pests.
Leave the clean shells to dry completely overnight.
Next morning, put the shells into a regular food processor, blender or coffee grinder. Crush them until you’re left with a coarse powder.
This powdered feed can then be sprinkled around the base of your plant on top of the soil. It will be absorbed into the soil when you water.
Alternatively, if newly planting or repotting, mix the powder into your potting compost. Make sure you give it a good stir to combine it well, and use around 5 powdered egg shells per plant.
Making egg shell ‘tea’ to use as liquid fertiliser
A different way, which is almost as simple, is to soak egg shells in water to make a sprayable or pourable liquid houseplant fertiliser.
Just boil up a couple of pints of water, take it off the heat and add in 5 washed egg shells.
Crunch them into pieces first to increase their surface area and help leach more calcium into the water.
Leave the water to steep overnight, strain out the shells the next morning and use in place of regular water.
If you’re pushed for time, an even easier approach (though the nutrient content won’t be as high), is to simply use the leftover water after boiling eggs.
If you’re used to having boiled eggs for breakfast, you can easily get into the routine of not throwing away your water.
I’m sure it goes without saying, but make sure you leave it to cool to room temperature before watering your plants. They won’t thank you for soaking them with boiling water!
Alternative method – equal parts egg shell and white vinegar
For those of you with an interest in chemistry, you might like this as there’s an actual chemical process at work.
Using cleaned and ground eggshells (prepared as above), mix one tablespoon of the powder with one tablespoon of white vinegar and leave overnight.
The acetic acid in the vinegar will react with calcium carbonate in the shells, visibly foaming and freeing up water-soluble calcium.
The mix is too concentrated to use by itself, so dilute it with a gallon (8 pints) of water and give plants a good soak. The free calcium will be readily absorbed by plants’ roots from the wet soil.
Which plants will benefit most from egg shells?
Any plant you’re growing indoors should benefit from the extra calcium in egg shell feed. But it will be particularly appreciated by edible plants, which are generally hungrier for nutrients than regular perennial houseplants.
Tomatoes especially, with their tendency to succumb to blossom end rot, are an ideal choice to supplement with egg shells.
And indoor-grown carrots and lettuce leaves may well be happier with a regular feed of egg shell water or powder too.
Over to you – never shell out on expensive fertilisers again!
Whichever method you choose, gardeners seem to agree that egg shells make a wonderful natural fertiliser for indoor plants.
100% natural, readily available and packed with calcium, there’s also some protein and other trace minerals in there too. All of which helps ensure plants are getting everything they need.
Best of all, they’re free and let you make great use of waste that would otherwise be thrown away. What’s not to love?!
Even if you have a go and don’t see much difference, you’ve lost nothing. So next time you make an omelette to feed yourself, you might want to save those egg shells to feed your plants too.
As ever, I’m always keen to hear your feedback on here. Have you tried using egg shells on your plants with fantastic results? How about middling results? Or even distinctly unimpressive results? Let me know in the comments!