Ferrous Sulfate 20% Iron is a high-purity ferrous sulfate heptahydrate (FeSO₄·7H₂O) supplying 20% soluble iron and 12% sulfur — a fast-acting, versatile single-ingredient amendment for correcting iron deficiency, supporting soil pH reduction, and managing lawn moss.
Iron deficiency (interveinal chlorosis — yellow tissue between green veins on new leaves) is usually a solubility problem rather than a supply problem: above roughly pH 7.0, soil iron converts to forms roots cannot absorb. Ferrous sulfate supplies iron already in the plant-available Fe²⁺ form, so foliar applications can produce visible green-up in new growth within days, and the oxidation chemistry that follows soil application gradually lowers root-zone pH — faster than elemental sulfur, which depends on slower microbial activity. It dissolves completely for foliar spray and soil application and also serves as an iron source for lawn moss management.
Ferrous sulfate works best in acidic to neutral soils; in persistently alkaline or free-lime calcareous soils a chelated iron source is more reliable, and it is not preferred for recirculating hydroponic systems, where Fe²⁺ precipitates out of solution. Important handling note: ferrous sulfate stains concrete, brick, stone, and fabric rust-brown on contact — sweep granules off hardscape immediately and rinse spray drift before it dries. Apply foliar sprays in cool conditions, wear gloves, and store sealed and dry, away from metal containers.
CDFA registered and third-party lab tested for heavy metals, with results consistently well below required limits.