Actino-Iron contains patented microorganisms that colonize on a plant's root system, protecting it from foliar and soil borne diseases. It also contains an organic iron that cures iron deficiency, promoting bigger, lusher, hardier and more vigorous plants. Simply mix into your soil when planting in containers or the garden. It can also be applied as a top dressing on established beds. A 3 pound bag covers up to 1,000 square feet of garden or treats 15 cubic feet of potting soil. Ideal for use on annuals, perennials, trees, shrubs and edibles. OMRI listed.