Steep the eggshells. Boil a gallon of water and add ten to twenty clean, dry eggshells. Let the shells sit in the water overnight, then strain them out. Pour two cups of liquid onto each plant. Repeat the eggshell tea process every two weeks.
Eggshells take a lot longer to break down compared to many other compostable goods, and too many of them can increase the acidity of your compost. This shouldn't be a problem, unless you plan on using it to grow plants that prefer low soil pH.
Which plants shouldn't you try this with? Don't add eggshell fertilizer to plants that prefer acidic soil, like blueberries. Ericaceous plants such as mountain laurel, pieris and azaleas also fall into that category. In extreme cases, low acidity for plants could impact their overall health and/or the resulting crop.
Because it takes several months for eggshells to break down and be absorbed by a plant's roots, it is recommended that they be tilled into the soil in fall. More shells can be mixed into your soil in the spring.
Jeff Gillman, Professor and author of several books including The Truth about Garden Remedies suggests using shells from 4 to 5 eggs per plant. Mix them in the garden soil or potting mix prior to planting.
Eggshells contain very few nutrients – mostly calcium. Most soil in North America has plenty of calcium. Unless your soil has a calcium deficiency adding more will not help grow plants. They also have a fair amount of sodium which is toxic to plants at even low levels.
Plants like tomatoes, peppers and eggplants in particular will benefit from shell fertilizer, Savio said. The extra calcium will help prevent blossom-end rot. Broccoli, cauliflower, Swiss chard, spinach and amaranth are also calcium-packed and could use extra from eggshells.
The shell of a chicken egg is comprised of about 96% calcium carbonate (CaCO3). Calcium is an essential plant nutrient and moderates soil acidity. Fast-growing plants deplete the soil of calcium very quickly so egg shells are an ideal supplement and feed for outdoor flowers, vegetables and fruit trees in your garden.
Also, on average, the plants with 1 gram and 5 grams grew taller than those without eggshell. However, the results also show that too much eggshell (10 and 15 grams) does not make the plant grow faster. Overall, I learned that a small amount of eggshell enhances plant growth.
Clean Eggshells are Safe Eggshells
Unless the only place the eggshells are going is into the compost bucket, I rinse them well and let them dry in a sunny windowsill.
You can simply add crushed eggshells in or on the soil as a natural way of providing your indoor plants with extra calcium. Another advantage is that the eggshells will also help to aerate the soil.
Just as when putting egg shells in planting holes, the more finely ground the powder, the faster the nutrients will leach down to the roots. For topical use, a good rule of thumb is to use about a tablespoon or two of pulverized egg shells per plant.
It's also said to help seeds germinate and repel slugs and other garden pests. But unless your soil has a magnesium deficiency, the University of Minnesota Extension Service recommends against adding Epsom salt. Too much can harm your plants and soil.
Banana peels can be placed directly onto pot plant soil, or around the base of your garden as mulch. As they decompose, they will release nutrients into the soil to feed plants. If using banana peels in your garden, place a single layer straight on top of the soil, being sure not to let them touch the plant stem.
Combine the two together, crush the eggshells by hand even more and sprinkle the mixture across the soil bed. Repeat the process every several months or at the start of a fresh growing season. The important thing is to not overdo it. Too much fertilizer can overwhelm and distress the plants.
Plant feed: Used tea bags double as a handy fertilizer because of their tannic acid, which in turn foster increased nitrogen levels. Many plants, including roses and potted plants, will benefit from the elevated levels, so mix or spread those steeped tea leaves right onto the soil.
In most cases, eggshells help improve the soil pH and increase or decrease it to a neutral level. For example, lavender does not enjoy acidic soil. If the soil in your region is acidic, mix eggshells in it to make the soil neutral and tolerable for the plant to grow properly.