How Earthworm Casts Affect House Plants

Nutrients

• Earthworm casts contain 5 to 11 times more nitrogen, phosphorous and potassium than garden soil. These nutrients are highly concentrated in the casts, and plants absorb them easily.

Soil Structure

• Earthworm casts increase the amount of aggregates in the soil. Aggregates are clumps of soil held together by organic matter and fungi. Aggregates stabilize the soil, improve drainage and increase the availability of oxygen, microbes and nutrients.

Results

• North Carolina State University advocates vermicomposting -- using earthworms to turn organic waste into compost -- based on the results of "The Potential of Earthworm Composts as Plant Growth Media," a paper by Clive Edwards and Ian Burrows. Their study showed that vermicompost, when added to peat or commercial potting medium, had a "profound effect on plant growth."

Use

• For seedlings, mix one part vermicompost to four parts potting soil. For established houseplants, top-dress with 2 tbsp. per quart of soil every two to four weeks.