Iron Sulphate for a Green Lawn

Iron Sulphate has many names and many uses around the lawn…

Iron Sulphate A.K.A. Ferrous Sulphate, Ferrous Sulfate, Sulphate of Iron or Soluble Iron

Courtesy of 'Mandalay'
Most lawn fertiliser products will contain nitrogen and potassium with phosphate coming in a close third. However, a few other elements are also required by the grass in micro or trace amounts. These are chlorine, boron, iron, manganese, zinc, copper and molybdenum.

It is rare for soils other than poor sandy soils to be deficient in these elements. Of them all, iron is perhaps the main one that you will add in the form of iron or ferrous sulphate. This is beneficial as a green-up or as a cool weather turf hardener; toughening the plant to resist disease. It is also the best way to get rid of moss which we will discuss in the topic ‘getting rid of moss’.

As a component of chlorophyll it imparts a dark green colour to the lawn so is very useful in cool weather when colour is more important than growth. However, only apply when ground moisture is available and keep the dose on the light side in the summer to prevent grass burn.

Some fertiliser manufacturers add iron sulphate to lawn feed products to give an extra bit of green to the grass. The problem with this is that many domestic lawn products then stain paths, driveways, patios and decking. In my opinion the very slight benefit is outweighed by the damage (the staining is permanent) you cause to other parts of the garden. Lawnsmith products apart from Winter Green do NOT contain iron sulphate for this reason.  Instead, seaweed, rich in iron and other beneficial properties is used.

The benefits of sulphate of iron:

  • Liquid application for adsorption through the leaves
  • Hardens the grass against potential disease – particularly late autumn and winter diseases
  • Component of chlorophyll so has a deep greening effect
  • Sulphur helps in plant functions and cold resistance
  • Slightly acidic promoting fine grass over coarse grass species
  • Acidity may reduce worm activity for a few weeks. Useful in the cooler months
  • It is the only lawn moss killer and will readily blacken moss
  • It can check many broadleaf weeds

A little caution:

  • Transient damage to grass if applied in dry conditions
  • Stains hard surfaces so can only be applied on turf
  • Transient damage or staining to your garden plants so watch where you spray

In summary, used correctly, iron sulphate is damn good stuff!