Quick Guide to Buying Moss Killer or Ferrous Sulphate
Ferrous or iron sulphate is the moss killing component of garden and lawn moss killers and also a constituent of some fertilisers. It is exactly the same chemical compound regardless of how it is sold or used. They may vary slightly in concentration and be mixed with other compounds but apart from that they are the same.
Ferrous or Iron Sulphate as Moss Killer
If ferrous sulphate is to be sold as a moss killer then the law requires that it is covered by pesticide legislation plus extra health and safety measures just as any pesticide should be. This adds to the cost!
This enables the manufacturer to advertise the product as a 'moss killer'. The concentrations are high enough to kill moss and low enough to cause the grass little or no damage. You will find these commonly sold as 'Moss Killer' or 'Lawn Sand'
Ferrous or Iron Sulphate as Fertiliser
Ferrous sulphate as a fertiliser is exactly the same stuff but sold for different purposes - usually for greening grass and hardening against frost and disease. The concentration to achieve this is usually lower than if used as a moss killer but pretty much every knowledgeable gardener and green keeper knows that it will do the same job as a moss killer at its higher permitted application rates.
Because it is not sold as a moss killer it is not required to be certified as a pesticide. This means it is much much cheaper but the benefit of being able to sell or market it as a 'moss killer' is lost.