Use Egg Shells and Coffee Grounds In The Garden To Maximize Success & Minimize Waste

5 comments by Halley -Author at MIGardener

Eggshells - The egg shell. I like to think of it as the unsung hero of the garden. Every year we throw out thousands of egg shells, and those shells go right into the land fill where they set and contribute nothing to society but build up the ever growing pile of trash. Let's change that! Egg shells are one of the best waste products for your garden. They provide beneficial calcium to your plants without hurting the pH like lime does. They break down slowly, providing a great source of slow release calcium all season long. They also help to restructure the soil to make it more porous and improve drainage.

So what do Eggshells do? By placing them below tomatoes, peppers, zucchini, and squash, the slow release of calcium will ensure that they do not suffer from blossom end rot otherwise known as (BER).  Blossom End Rot occurs when the plant is lacking calcium. Eggshells also help to deter slugs. When placed around your plants, hungry slugs will try their best but the sharp edges of the eggshells will create a barrier of protection around your plants. When buried, the eggshells as mentioned earlier will help drainage and aeration in the soil.

How to use eggshells in the garden?  Many people are concerned about using eggshells for fear of salmonella. A sure fire way to eliminate the risk of salmonella, is to place the egg shells in the oven at 300° for 5 to 10 minutes. Once eggshells have been sanitized you can place the eggshells in a food processor to convert them into a powder which can be used as a fertilizer for your plants (the finer the eggshells are ground, the better they can be absorbed.) You can also crush them using your hands and use them around the base of plants to protect them from squash.

Do they smell? Eggshells do not smell at all once they have been washed. NOTE - This is critical! Unwashed eggshells will smell sulfuric and nasty, but a quick rinse in the sink will make sure there is almost zero smell. Further, once they have been sanitized in the oven this will even further reduce the smell that may be left.

Want to read more about Calcium in the garden and the role it plays? Read this blog post we wrote! about the role calcium plays in the garden.

Coffee Grounds - Every year the average household will throw out 20 pounds.. yes. 20 POUNDS of coffee grounds. The average coffee shop throws out 500-1000 pounds of coffee grounds. This waste product is thrown out by everyone and they have no idea about the precious material they are throwing out! Coffee grounds are rich in organic matter, high in nitrogen, phosphorus, and potassium.

What do coffee grounds help with? Coffee grounds are rich in an organic source of Nitrogen, phosphorus, and potassium. The NPK of coffee grounds are (2-.03-.03) meaning 2% of weight is Nitrogen, .03% is Phosphorus, and .03% is Potassium. Coffee grounds also are rich in organic matter meaning they help to build the soil, add porosity, and increase drainage and aeration within the soil. They can be used in the compost pile to balance the carbon to nitrogen ratio. There is also some evidence that suggests the addition of coffee grounds will help provide a home for beneficial fungus and bacteria which are needed in the garden.

Do coffee grounds acidify the soil? This is an urban legend and an old wives tale. Adding used coffee grounds will NOT acidify the soil at all since the acid is washed out of the grounds in the coffee making process. Old or stale coffee grounds can increase soil acidity, but only slightly. This means that adding coffee grounds will not help plants that need a low pH soil like blueberries or potatoes. But they will still receive the benefits of the added nutrients.

Want to read more about Nitrogen in the garden and the role it plays? Read this blog post we wrote! about the role Nitrogen plays in the garden.


  • Antonio Delfin

    Thks very informative.

  • Evelyn Risse

    I put a pinch of baking soda in my coffee pot before perking it. I assume trace baking soda in the coffee grounds won’t hurt anything?

  • Bella Morano

    I am doing a project at school and I was wondering if it will work on plants you eat also and doesn’t affect their taste?

  • Jesse

    I’ve read that adding used coffee grounds to soil can cause mold. After I make a cup of coffee, what should I do with the grounds? Do you freeze or dry them? Can you add them directly to the soil? Thanks!

  • Dave

    Great information, and put my mind at ease!

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