Lawn Care Experts
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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 material 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 Sold 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 Sold as Fertiliser

Ferrous sulphate sold 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.

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When can I apply to moss?

  • Anytime after mowing
  • At least 3 days but preferably 5-7 days before next cut
  • Avoid strong sun, frost and freezing
  • Give a 7 day gap if using weed killer (before or after)
  • If raking or scarifying you can use before and/or after - 4 weeks minimum between applications
  • If seeding apply at least 2 days before seed

DO NOT spray on grass less than 6 months old at full strength. A half rate or lower is safe.

Can I mix with other products?

Ferrous Sulphate can be mixed in the same container as our soluble fertiliser. You can also apply ferrous sulphate at the same time as applying granular fertiliser.

Do not mix weed killer with moss killer or ferrous sulphate. If you need to kill moss AND weeds do it about a week apart.

When seeding, you can spray ferrous sulphate on the lawn 1- 2 days before applying grass seed.


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