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Are Eggshells Good For Hydrangeas?

Usage of eggshells is a widespread practice because everyone wants to get as much efficiency as possible from everything we deal with. This is especially true for the garden because ornamental plants need constant fertilization for a better appearance.

Eggshells are good for hydrangeas because it contains calcium, making the plant stronger and improving growth. However, this only works if the shell is ground into powder.

Besides, eggshells have another effect that you need to know about. This effect and much more will be discussed below.

How to use eggshells properly?

It is a mistake to use eggshells in uncrushed form. This also includes coarsely ground eggshells.

In fact, big pieces of eggshells can retain their shape and not decompose over the years, so the only way to benefit from them is to grind to a powder. The smaller the particles in the powder, the easier they will decompose in the soil.

High acidity is required to decompose a large piece of eggshells. No soil has this level of acidity. On the other hand, microparticles of eggshell powder decompose quickly at relatively low levels of acidity.

Read also: Which hydroponic system is best for strawberries?

Make powder

To make the powder, you need to collect the shell of at least ten eggs. Then it should be washed in clean water and left for a while to dry.

Then place the eggshells in the oven to bake it a bit. This is needed to kill the pathogenic bacteria (salmonella).

The oven temperature should be 212 ° F (100 ° C), hold the eggshells there for 1-2 minutes, and then remove. If you keep them longer, then they can burn, and you will not succeed.

In fact, Salmonella bacteria are quite a severe health threat, so if you do not destroy them, they can spread to you in the garden.

The next step is to grind the eggshells. Use a blender or coffee grinder for this. Mortar and pestle are also suitable, but you have to make a lot of effort to get the desired result.

Grind the eggshells as finely as possible. The microparticles will dissolve quickly and improve the soil.

Place the finished product in a plastic container and transfer it to a dry place.

The best time to apply eggshells powder is spring. At this time, the humidity is relatively high, and the particles are washed away by water around the plant.

Besides, the hydrangea begins to grow at this time, and it needs trace elements to form new vigorous shoots.

Pour 3-7 oz (100-200 g) of powder evenly under each bush. This amount is quite enough. If you pour more, nothing will happen; there will not be enough acidity in the soil to decompose a large amount of calcium carbonate.

One top-dressing a year will be enough for healthy growth. It makes no sense to apply powder in summer, especially in autumn, because hydrangeas do not grow at this time so that it will be just a waste of material.


The next thing you can do with eggshells is to add them to the compost. Of course, they must be baked and ground into powder, as I wrote above.

For the basis of compost, it is better to choose shredded branches of young trees. This raw material contains the most nutrients for the plant. Besides, young plants get sick less, so there will be fewer spores of fungi and bacteria.

You can also add other ingredients to the compost, such as kitchen scraps. However, I do not recommend adding a lot of animal residue, which leads to the development of many bacteria.

Next, add the eggshell powder to the compost. Its amount should not exceed 5-10% of the total mass. Then mix everything well.

Leave the compost for a year to decompose.

The compost pile should not be too high. Each layer must have access to air.

Otherwise, without air access, fermentation processes will begin; thus, the compost will be saturated with aggressive substances harmful to plants.

The compost will become slightly acidic in the decomposition process, which will help dissolve the eggshell powder.

As a result, you get an excellent organic fertilizer for hydrangeas.

Do eggshells affect soil ph?

The eggshell powder can change the soil pH, but only if the soil is acidic. Only sufficient acidity can dissolve the calcium contained in the shells.

If you add a significant amount of eggshell powder to acidic soil, it will become neutral. And as soon as the soil pH reaches 6.8, the powder will no longer affect the soil’s acidity.

Gardeners seek to change the acidity of the soil to get the desired color of flowers.

When you add the powder to the soil, you will make it neutral, i.e., the color of hydrangea flowers will be purple. To get a different color, you need to add other elements to the soil.

The most popular blue color of hydrangea can be obtained by adding aluminum sulfate to the ground. This will acidify the soil and increase the amount of aluminum there.

However, in this case, adding eggshell powder does not make any sense because it neutralizes aluminum sulfate’s action.

To obtain a pink color, the soil must be alkaline. As I mentioned, the powder will not make the soil alkaline (only neutral), so you need to apply garden lime for pink flowers.

Changing the soil’s acidity will take some time (about a year), and the color change takes even more time, so be patient and continue to care for your plants.

You need to add other elements to the soil

The eggshell powder can provide plants with a small amount of calcium. This means that eggshell powder can only serve as an auxiliary source of this element.

If your plants need a lot of calcium in the short term, you should add to the soil garden lime or fertilizer with the high calcium content. In this case, you will achieve the result quickly.

For the eggshell powder to dissolve constantly, you need to keep the soil slightly acidic. This can be achieved by mulching hydrangeas. 

But if the soil is alkaline the leaves may turn yellow, to solve this problem please check out this article.

Mulch will eventually decompose with beneficial bacteria, and the soil acidity will increase (what you need). As a result, you get fertilizer from mulch and eggshell powder.

The best mulching material is compost. In addition to organic fertilization, it will not allow the soil to dry quickly. Also, mulch will create an obstacle to the sun, and the earth will not overheat in summer.

Applying eggshell powder does not mean that you do not need to feed your hydrangeas. These plants need a lot of energy for lush flowering.

I recommend adding slow-release mineral fertilizer in addition to organic fertilizer (compost mulching).

There are many good fertilizers on the market with different NPK formulas. Choose a product that contains more phosphorus than the other two components. Phosphorus is responsible for the formation of flowers so that you will get a lot of beautiful inflorescences.

Useless methods

In conclusion, I want to say a few words about the ineffective methods of using eggshells.

The first is soaking the shells in the water. Many believe that after such soaking, the calcium content in the water increases. And allegedly watering plants with this water, you can get good results.

Unfortunately, this is not true. Soaking the eggshells almost does not change the water’s mineral composition. The amount of calcium released into the water is so meager that it is not worth the effort.

The same applies to the boiling of eggshells in water. All these are myths that should not be believed.

The second useless way is to dilute the eggshell powder in water and spray this solution on hydrangea leaves.

As a result, you won’t achieve anything. The leaves are not able to absorb calcium in this form. All you get is white powder-coated leaves.