Cast 'N Frass Organic Fertilizer COmpany offer 100% pure worm and cricket castings. All natural organic worm castings are the richest fertilizer known to man. Worm Castings are full of nutrients and essential minerals that promote plant growth, including concentrated nitrates, potassium, phosphorus, magnesium, and calcium. Use as an enriching soil amendment or as a top-dressing. A small amount goes a long way! Even just a tablespoon of pure worm castings offers enough organic nutrients to feed a 6" potted plant for more than two months.