Amy Draiss
Some garden hacks acquire a reverential status, and we may use them without fully knowing why. As a gardener who has enjoyed many successes (but seen my share of failures), I’ve often been told about the benefits of using eggshells for plants, as though I was being gifted special VIP access to some magical plant wisdom.
Maybe you've heard of the beneficial properties of eggshells in gardening, for everything from slug traps to compost enhancements. Now I’m not going to dissuade you from ever using eggshells – and I’m all for organic gardening with recycling household waste in a safe and practical manner. But if you aren’t careful, you could be using eggshells in the wrong ways, potentially compromising the health and growing potential of plants.
This checklist isn’t designed to cause alarm, but rather to encourage you to use eggshells in a sensible way. If you scatter them willy-nilly around your garden, this article is for you. Don’t worry, you can still turn those shells to good use. It’s just a question of making sure you prep them appropriately and utilize them correctly. As the saying goes, you can’t make an omelette without breaking some eggs. But you can improve your gardening successes by using eggshells in a more thoughtful manner.
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Are You Using Eggshells For Plants Correctly?
Eggshells naturally contain a high amount of calcium carbonate, and this ingredient is often mentioned as being beneficial in the garden, particularly as a soil amendment. While calcium can be enormously beneficial to plant growth, a couple of eggshells tossed around your plants won’t necessarily be harnessing the goodness of the shell – and it certainly isn’t an easy fix for just any plant in need of a growth spurt. For one thing, getting the calcium out of the shell and into the plant requires a particular process. For another, there are certain things in eggshells that might work against specific plants in your garden.
One hack you might have seen involves scattering eggshells around the base of plants to reduce the risk of blossom end rot. Again, this is to do with calcium in the shell. While blossom end rot is often associated with a lack of calcium, it doesn’t follow that you remove all risk by dropping eggshells around young plants. Timing can be critical in prepping the soil for optimum growing conditions – there are seldom going to be easy shortcuts if you haven’t prepped properly in the first place. Diseases like blossom end rot can often be as much to do with watering irregularities, soil pH problems or root damage, which could be preventing adequate calcium uptake in the roots or the soil.
With the following eggshell mistakes, I want to encourage a sense of taking all the necessary steps to ensure that plants grow in the safest and healthiest way, trying to stick to a sensible care routine, respecting the wishes of each plant – and proceeding with moderation and caution. Without wishing to take the fun out of trying out a few hacks here and there, it’s much better to follow a thoughtful routine tailored to each plant, from the beginning. So, here are a few classic uses for eggshells that can lead to mistakes. Hopefully, it’ll give you some food for thought on how you can better use your stray shells in your growing plans.
1. Using Eggshells to Tackle Slugs
One of the big uses for eggshells in a garden is in combating slugs and snails. It’s understandable to reach for any methods for keeping these pests away from plants. Nobody likes to see their hard work getting chomped by gastropods, I get it. Desperation can lead us to do crazy things – and that old advice about sprinkling eggshells around plants to create a barrier seems to have an element of persuasion. Unfortunately, the idea that eggshells will keep slugs and snails at bay is flawed.
According to the findings of trials conducted by the UK’s Royal Horticultural Society, amongst others, the use of eggshells can be unreliable and ineffective. Molluscs are adept at navigating coarse and pointed terrains thanks to their mucus secretions. Adding eggshells as large pieces will create gaps for slugs and snails to squeeze their way across. Even if you are willing to crush the shells up and create more sharp edges in greater volumes, this is far from a perfect solution. Relying on eggshells in the garden as your only slug buster is a recipe for disappointment.
For those in search of organic snail and slug controls and deterrents, there are far better measures you can try. A slug pub comprising a dish or bowl filled with beer is generally more effective as a way of managing slug numbers, particularly if used in tandem with other methods, such as nematodes. You can also get baits that target molluscs while being safe for pets, such as Bonide Captain Jack’s Slug Magic Granules from Amazon. Alternatively, sprinkling diatomaceous earth, such as Harris Diatomaceous Earth 4lb from Amazon, around plants can control slug numbers by causing them to dehydrate.
2. Using Eggshells with Acid-Loving Plants
Are eggshells always good for the garden? You may have seen eggshells dusted around plants to help “give the earth a boost” and figured where’s the harm in trying it yourself? The allure of a calcium boost may seem harmless enough. Unfortunately, if you are growing acid-loving plants like rhododendrons, azaleas, camellias or crops like blueberries, a mass scattering of eggshell is far from ideal. That high calcium content actually acts as a moderator in soil, and over time it can reduce acidity levels. It won’t necessarily be an instant issue – but once that calcium starts building up in the soil, it’s only a matter of time.
In extreme cases, the presence of eggshell where you grow acid-loving plants – and the buildup of calcium from eggshells in garden soil – can create a barrier between the plant and specific nutrients it needs to absorb. If in doubt about your soil pH, it’s wise to test the soil by using a soil meter, like the Raintrip 4-in-1 Meter from Amazon. If you need to raise the level of acidity in your soil, add a fine granular elemental sulfur in the fall, like Earth Science Fast Acting Sulfur from Walmart. Test the soil again, and once you are happy with acidity levels, aim to use eggshells only in places where you can be sure they won’t cause issues to acid-loving plants.
3. Using Eggshells As Pots for All Seedlings
The sight of a seedling growing out of an eggshell is undeniably life-affirming, and I must admitI have given this one a go. It’s not that it’s always a bad idea. But again, it shouldn’t be used across the board for all plants. When mulling over eggshell uses in the garden, you may well be scratching your head at this one and wondering how an iddy-biddy eggshell pot can possibly harm a seedling. It comes down to a little research into the plant you are starting from seed – specifically, how fast it is likely to germinate and grow in those first few weeks, and how deep its roots are likely to be.
For some crops, like cress, there are no issues with eggshell pots, since the roots are so shallow and the space they take up so negligible, even with multiple seedlings. However, for crops such as carrots and parsnips with longer tap roots, it’s easier for seed-starting mistakes to happen. Using a compact and irregular shaped base for deeper-rooted seedlings can lead to twisted or stunted root systems, compromised and potentially incapable of reaching maturity. Fast-growing seedlings such as beetroots and sunflowers can soon require more space than is feasible in the narrow confines of an eggshell pot.
If possible, it’s best to grow deep-rooted seedlings directly in the earth (making sure you have removed larger chunks of soil debris first). Where that isn’t possible, grow deep-rooted seedlings for crops such as carrots and beets in tailored cell trays and propagation kits. You can buy deep cell propagation trays such as Rootrainer 32-Cell Kits from Amazon.
How To Use Eggshells In The Garden Safely
My introduction to eggshells as a gardening aid, many years ago, is probably still the most reliable way to use them – and that is as part of a thoughtful, well timed composting routine. Whether you are planning on making compost via the traditional heap in the corner of your garden, or by way of a composting bin, the shells make an egg-cellent (sorry, couldn’t resist that one!) addition to a broader mass of well selected browns and greens. However, just because there’s safety in numbers, that doesn’t mean you are ok to throw the shells straight into the compost without having a few things checked off first.
If you have designated eggshells in the compost, make sure you have washed them thoroughly. This is important both as a way of neutralizing odors (so reducing the risk of attracting vermin) and minimizing the chances of transferring pathogens to the compost heap. Second, ensure that the shell particles are as small and finely crushed as possible. Leaving shells in two halves, sitting forlornly on the top of a pile of rotting vegetable matter, is no good – it can take a year or more for full shells to decompose. Crushing shells guarantees that all micronutrients will be absorbed into the compost as quickly as possible.
Crush your shells using a pestle and mortar like the highly rated ChefSofi Granite Mortar And Pestle Set from Amazon, or a blender such as the Vitamix Explorian E310 from Amazon. Eggshells can also be great if you are vermicomposting, as worms love them. They are beneficial to a worm’s digestive system and can help neutralise acidity levels in the worm bin. The Gardening Know How team loves the Vego In-Ground Worm Composter Bin from Amazon. Again, just make sure the eggshell pieces are as finely crushed as possible, and also that you use this compost in the right places in your garden.
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