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How many compost bags?

40 sq ft in greenhouse at about 3 inches deep plus 8 x 10 inch pots.  How many 25 litre bags should I need?  Who's clever at maths? 


  • According to these online calculators I need a lorry to visit the garden centre, 43 small bags can't be right, surely? 
  • FairygirlFairygirl Posts: 53,966
    Why 25 L bags and not bigger ones  though?  :)
    Most are about 60 L now. 
    You can usually get a bulk delivery too - far cheaper  :)
    Sorry - haven't worked out the volume yet....
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • hogweedhogweed Posts: 4,053
    For your bed I get 324 litres which is about 13 bags of 25 litres plus the extra for your pots - say a pot is about 5 litres so that's another 2 bags - so 15 bags in total would be my guess. 
    'Optimism is the faith that leads to achievement' - Helen Keller
  • Mr. Vine EyeMr. Vine Eye Posts: 2,385
    I work that out as 11-12 bags for the greenhouse

    and 2 bags for the pots

    so 14
    East Yorkshire
  • FairygirlFairygirl Posts: 53,966
    I make it 284 litres for the greenhouse, so about 12 x 25 litre  bags. A couple of bags for the pots, in theory. Make it three - compost settles  :)
    15 in total. 
    But much cheaper to get bigger bags....
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • AlchemistAlchemist Posts: 273
    edited October 2018
    280 litres for 40ft2 and ~4litre/pot. Apologies didn’t realise this has been answered hence the edit. 
  • AlchemistAlchemist Posts: 273
    Wyevale had 3 for 2 on their 125l multi purpose a few weeks ago. This should sort you out assuming you can carry (it’s quite hefty). 
  • Fairygirl:  After 50 litre bags gave me a hernia in February I'm sticking to the smaller ones!
    hogweed and Mr.Vine Eye:  Thank you, and Alchemist.
  • LynLyn Posts: 22,865
    Bags of compost from the GH isn’t a lot of good, nutrients for only a few weeks, you’ll need to feed it up and then probably have to  change it all next year.

    With mine I have half full of garden soil,  then home made compost on top, I don’t think you have a compost heap do you? If not you’ll need to buy some, but not as many as filling it up with the stuff, then I buy 3 Tomorite grow bags a year and mix it all together. 
    You may be better buying in some top soil if you can’t spare it from you garden. 
    Gardening on the wild, windy west side of Dartmoor. 

  • DovefromaboveDovefromabove Posts: 86,102
    I wouldn't use any multi-purpose type compost at all for that sort of thing ... I'd use topsoil (bagged from the GC if I didn't have any) mixed with bagged soil conditioner (also from the GC) if I didn't have any home made compost.  

    MPC turns to dust within a few months. 

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

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