Espoma Organic Traditions Rock Phosphate is a 100% natural source of phosphorus. Plants require this nutrient for healthy root development and for fruit and flower production. 
Mined from natural rock with phosphorus-rich deposits, Espoma Rock Phosphate is washed to eliminate clay impurities and then heated to remove moisture. Rock Phosphate is ground to such a fine powder, an efficient part of it is immediately available to your plants.
As your plants' roots give off carbon dioxide and certain organic acids that react with the Rock Phosphate, the fine powder makes the phosphorus available for plant use as needed, resulting in a long-term, slow-release nutrient source.