Dave Thompson’s Organic Healthy Grow Worm Castings provide an excellent way to soften soil and increase microbial activity while giving plants a natural, easily absorbed source of nitrogen, calcium and iron. This results in faster growth, larger plants and bigger blooms. OMRI listed. Use only single-sourced worm castings from a temperature and moisture-controlled environment in which the worms are counted and weighed every two weeks to ensure over 95% pure castings