Weedol and ferrous sulphate

Posts

• Obelixx Posts: 30,090

  September 2020

  Weedol is indiscriminate and will kill grass too unless you have the specific lawn weed killer version.
  
  I personally would not mix garden chemicals.   Asking for trouble but then I'm not a chemist and I don't care about weeds in the grass as they add to biodiversity for all those teeny, invisible but essential critters that make for a good wildlife balance and, when we have one of the increasingly frequent droughts, sometimes they're all that's green.

  Vendée - 20kms from Atlantic coast.
  

  "The price good men (and women) pay for indifference to public affairs is to be ruled by evil men (and women)."

  Plato
  

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• Dovefromabove Posts: 88,147

  September 2020

  Only use specific lawn weedkiller on your lawn ... other weedkillers will kill the grass too 😢

  
  Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
  
  
  
  
  
  

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• julietate Posts: 3

  September 2020

  The Weedol is a lawn weedkiller (at least that's what it says on the box).
  
  I have plenty of areas for wildlife but I'd like a lawn as well!

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• Dovefromabove Posts: 88,147

  September 2020

  Ok ... Weedol make several different weedkillers. 

  
  

  I still wouldn’t mix chemicals without running it past the manufacturers. 

  
  

  I would prefer to use a combined Autumn lawn treatment specifically formulated to be used in one application. 

  
  Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
  
  
  
  
  
  

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• BobTheGardener Posts: 11,385

  September 2020 edited September 2020

  The general rule of thumb is to never mix garden or household chemicals as there's a good chance that one will deactivate the other (or worse.)  In this case, Ferrous Sulphate is very acidic (pH approx 2) and that acidity may simply break-down the active chemicals in the weedol.  I just looked-up one of the weedol lawn weedkiller ingredients (fluroxypyr) and that is only stable within a pH range of 4 to 7, so would probably be destroyed by the Ferrous Sulphate.

  Highly technical link about fluroxpyr:
  

  https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/347.htm

  
  

  A trowel in the hand is worth a thousand lost under a bush.
  

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• julietate Posts: 3

  September 2020

  Thanks Bob, that's very clear and understandable. It never occurred to me to think about one deactivating the other. I guess it makes sense to use the Weedol first, let it get taken up, and then use the ferrous sulphate at a later date. Many thanks.

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