Ferrous sulfate, commonly known as iron sulfate, is a micronutrient supplement used in lawn care to enhance visual appeal. Its primary function is to supply iron, a cofactor in the synthesis of chlorophyll, the pigment responsible for the plant’s green color. Applying this compound corrects iron chlorosis, a condition where grass blades turn pale green or yellow, especially in alkaline soils where iron is unavailable for absorption. This treatment provides a rapid green-up effect, giving the turf a deep, lush color without promoting the excessive growth caused by nitrogen fertilizers.
Identifying the Right Formulation
Before purchasing, understand the differences between granular (dry) and liquid formulations. Granular iron sulfate offers a longer-lasting effect, releasing iron over four to six weeks. However, granules must dissolve into the soil, and there is a risk of oxidation, making the iron unavailable, especially in alkaline soil.
Liquid iron sulfate, often prepared by dissolving the dry material in water, provides a much faster, immediate green-up response. This occurs because the iron is absorbed directly through the leaf tissue via foliar feeding. This effect is temporary, usually lasting only a couple of weeks, requiring more frequent application for sustained color.
When examining product labels, the analysis tag specifies the percentage of elemental iron (Fe) present, which determines efficacy and application rate. Common concentrations range from 20% to 30% iron sulfate. The two main chemical forms are ferrous sulfate heptahydrate and ferrous sulfate monohydrate. The heptahydrate form is a highly water-soluble, blue-green crystal ideal for liquid sprays, while the monohydrate is a lighter powder or granule.
Retail and Online Sources
Iron sulfate is available through several retail channels catering to different volume and product needs.
Big-box home improvement stores and farm supply centers are reliable sources. They frequently stock granular products in large bags, often 40 to 50 pounds. These stores commonly feature concentrated powders or granular formulas, such as 30% iron sulfate monohydrate, suitable for broad application across larger lawn areas.
Local suppliers, including independent garden centers, nurseries, and agricultural supply stores, often provide more specialized or bulk options. These locations may carry the product in smaller, four-pound containers convenient for residential use or targeted treatments. Local agricultural suppliers may also offer professional-grade concentrations or bulk quantities.
Online vendors, including large e-commerce platforms and specialty lawn care websites, offer the widest variety of iron sulfate formulations. Purchasing online allows access to both liquid concentrates and bulk granular bags, often in 50-pound sizes. This avenue is useful for sourcing specific chemical forms like the highly soluble heptahydrate powder for spray applications.
Safety and Storage Guidelines
Handling concentrated iron sulfate requires specific personal protective equipment (PPE) to prevent irritation and exposure. Users should wear chemical-resistant gloves, such as neoprene or rubber, and safety goggles with side shields to protect the eyes from dust and splashes. A dust mask or respirator is recommended when handling the dry, powdered product to avoid inhaling fine particles.
The iron compound is highly prone to causing rust-like stains on porous surfaces. Any spills of powder or liquid on concrete, stone patios, or driveways must be swept or rinsed immediately before the product sets. Once a stain has oxidized and dried, removal often requires specialized acidic cleaners, such as those containing phosphoric acid.
For storage, iron sulfate must be kept in a cool, dry, and well-ventilated location away from direct sunlight and heat sources. The container needs to be tightly sealed, as the product is hygroscopic and will absorb moisture. This absorption leads to clumping and reduced effectiveness. Store the product securely away from children and pets, as ingestion can be toxic.