Eggshells in the garden: magic solution or placebo?

Article for :Beginner and plant killerExperienced plant lover

Some marabouts can fix your computer and bring back your loved one in less than 48 hours. Eggshells have nothing to envy them, if you listen to many gardeners. It's said to turn your soil into fertile soil, repel slugs and cure disease. But should we really believe it?

Eggshells are an excellent fertilizer

We all dream of an effective, organic and free fertilizer - Photo by Ivan Radic / Flickr

Eggshells are an excellent natural fertilizer. At least, that's what my grandmother, my neighbor and half the gardeners on the Internet think. For healthy plants, all you have to do is grind eggshells to a powder and, as you wish :

place them at the foot of the plants ;
bury them in the planting hole ;
mix them with the soil.

At first glance, using eggshells to fertilize plants seems like a pretty good idea. In fact, 95% of a hen's eggshell is calcium carbonate, crystallized in the form of calcite. And it's a well-known fact that plants need calcium to grow.

But the reality is more complicated. Shells take a long time to decompose. In soil with a classic pH, such as that found in our gardens and vegetable patches, it takes several hundred years for the shell to turn to dust. In Israel, archaeologists have found hen's egg shells over 2,600 years old that had not yet decomposed!

So you'll need to be patient if you want to fertilize your plants with eggshells. It will take several centuries for your roses, peonies, tomatoes and eggplants to benefit from the calcium released by eggshells.

Don't like waiting? Instead, use a calcium-rich fertilizer to fertilize your plants, and set a reminder in theMonstera app to make sure you don't forget.

Eggshells can neutralize acid soil

Some crops can modify soil structure - Photo by John Moore / Flickr

The high calcium content of eggshells can also modify soil pH. Crumble up some eggshells and bury them to transform acid soil into more hospitable soil.

Here again, the main flaw in the plan lies in the slowness of the decomposition process. While acidity speeds up decomposition, you'll still have to wait two or three years for your shell to disappear in very acid soil, with a pH of 4..

But even if you're very patient, you'll have to deal with another problem: the quantity of eggs to use. To change your soil type permanently, you'll need hundreds or thousands of eggshells, depending on the size of your garden!

Fortunately, there are more effective solutions for improving the pH of your garden. If your vegetable garden is too acidic, for example, you can amend the soil with calcareous matter (dolomite, wood ash, agricultural lime, etc.) or lime it. Finally, planting millet or lupins helps to correct the structure and composition of the soil.

Eggshells repel slugs

Collecting is one of the most effective ways of getting rid of slugs and snails

Eggshells are the guardian angels of our vegetable garden and flower beds. Roughly crushed, they form an impenetrable natural barrier to slugs and snails. Their sharp texture would injure the gastropods, preventing them from gaining access to our vegetables and flowers.

Many gardeners have believed this horticultural myth, only to find their lettuces and tomatoes devoured in the early hours of the morning. Slugs and snails have no use for eggshells. They secrete a mucus that protects them and enables them to cross this barrier.

If you want to protect your plantings from gastropods, forget grandma's recipes. Use netting or slug pellets instead. You can also set up a dedicated area in your garden, with shelter and food, to keep them away from your vegetable garden.

Eggshells cure peach blight

Leaf curling is one of the symptoms of peach blight - Photo by Tsaag Valren / Wikipedia

Eggshells are also said to combat peach blight. Evidence of this can be seen in the nets filled with eggshells hanging from tree branches.

Peach blister or almond blister is a fungal disease caused by a fungus. Contrary to popular belief, it does not develop when the soil is poor in calcium, but when the weather is wet and temperatures exceed 10°C. This is why symptoms often appear in spring.

Decorating your fruit trees with eggshell garlands will therefore have no effect. The symptoms and the fungus will disappear in summer, when showers become rarer and the weather warms up. If you want to combat peach blight and almond blight effectively, opt for preventive measures instead:

plant resistant hybrids and cultivars;
fertilize and prune your trees to keep them healthy and less vulnerable;
remove blistered leaves to prevent the spread of the disease.

Eggshells combat blossom end rot

Mulching indirectly combats blossom end rot - Photo by Arpent nourricier/ Flickr

Burying eggshells at the bottom of the planting hole for vegetables and tomatoes is said to be the natural solution to combating blossom end rot.

Blossom end rot is linked to calcium deficiency in plants such as tomatoes, squash and peppers. Providing calcium through eggshells would help prevent the phenomenon.

There are two arguments against this. Firstly, eggshells take forever to release the calcium they contain. What's more, in the case of black ass, the lack of calcium is not due to a lack of calcium in the substrate. It's linked to the plants' inability to absorb it. More often than not, this difficulty is the result of irregular watering. When the plant lacks water, the sap doesn't reach the fruit, which rots.

To combat blossom end rot, make sure your plants are not suffering from water stress. Water both potted and outdoor plants regularly. Don't hesitate to mulch the soil to keep it moist between waterings.

How to use eggshells in the garden?

Next topic on the blog: seeding in an eggshell, cute or hideous? Photo by Xoyos / Flickr

Would you like to recycle your eggshells in the garden? The best solution is to add them to your compost. You can then use them to fertilize your flowers, trees and vegetable garden. Remember to crumble them beforehand to encourage decomposition. And don't over-proportion them to other organic waste, to help them assimilate.

Eggshells are also an excellent food supplement for chickens! In fact, in order to produce their shells, which are so rich in calcium, laying hens need... Calcium. If you have your own hen house, crush the shells and offer the pieces to your chickens to enrich their diet.

Finally, some gardeners like to use eggs instead of plastic cups for their seedlings. Simply empty the cup, drill a hole in the bottom of the shell, fill with substrate and plant seeds. This technique offers no added value in terms of gardening, but it can save you the price of a seedling tray and add a quirky touch to your decor.

By Servane Nemetz
on 24-02-2025 at 09h20