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How much compost?

HalesowenmumHalesowenmum Posts: 22
in Garden design
Hi.

I've got a planter this size:
400 x 80 x 81 cm
and I'm not sure how many litres of compost do I need?

Can anyone kindly advise?
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Posts

  • fidgetbonesfidgetbones Posts: 17,618
    2.592 cubic metre.  If you are having it delivered in builders bags you will need three.
     1 cubic metre is 1000 litres, so 2,592 litre.
    if 60L compost bags is 43.
    40L compost bags is  65.

    That is hell of a big planter.  What are you planning on growing in it?


  • ElferElfer Posts: 329
    edited May 2021
    You'd probably want to leave a few centimetres empty at top

    400x80x78/1000=2496 Litres 

    So approximately 2500L is what is required to fill your planter but if you are going to add garden soil or grit to your compost then you need to adjust.
  • HalesowenmumHalesowenmum Posts: 22
    Thank you so much.

    So if it was in the form of 20 litre 'regular size' bags of compost, that's what, 125 bags?

    I know that's probably absolutely right - but it just sounds like so so much 😅!

    I don't think I can use a bulk bag delivery because they'd deliver it to my drive and it would be hours of work to transport it round to the garden via the rear path.





  • HalesowenmumHalesowenmum Posts: 22
    I should probably also ask what type of compost, and would I need anything that's more like a fertiliser / top dressing type element as part of what I buy (you having mentioned soil)?

    It's going to be 4 essentially hardy perennials, there's a rose, some grasses, and then some of your typical cottage garden staples like delphiniums lupins that kind of thing. 

    I was thinking peat-free but would be interested to hear thoughts.
  • FairygirlFairygirl Posts: 55,117
    You need a soil based medium, not compost on it's own. It won't have enough sustenance for plants that are in there long term. You could probably put a layer of rubble or similar in the bottom to save money, as it's a deep planter.
    If you had some spare turf, that works very well. I did that with all my raised beds as I was removing an area of compacted turf from the boundary of the garden. It's ideal for long term planting. 
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • HalesowenmumHalesowenmum Posts: 22
    fidgetbones said:
    2.592 cubic metre.  If you are having it delivered in builders bags you will need three.
     1 cubic metre is 1000 litres, so 2,592 litre.
    if 60L compost bags is 43.
    40L compost bags is  65.

    That is hell of a big planter.  What are you planning on growing in it?


    Apologies, the site hasnt been updating to show me all replies.

    Yes it is big!

    It's going parallel to the fence on one side of the garden and effectively that will be my only plant-growing area apart from some pots on a patio. The rest is just plain lawn so I've got to fit in all my cottage garden type planting into that one receptacle!
  • HalesowenmumHalesowenmum Posts: 22
    Fairygirl said:
    You need a soil based medium, not compost on it's own. It won't have enough sustenance for plants that are in there long term. You could probably put a layer of rubble or similar in the bottom to save money, as it's a deep planter.
    If you had some spare turf, that works very well. I did that with all my raised beds as I was removing an area of compacted turf from the boundary of the garden. It's ideal for long term planting. 
    Ooh, good idea about stuffing the bottom with turf. I'll ask the garden man to save some of it for me.

    In searching for the right product, what wording am I looking for - I think I've only ever bought compost before I don't think I've ever brought any soil as such so I'm a bit clueless on that.
  • FairygirlFairygirl Posts: 55,117
    You can buy loam based composts. It's a formula - John Innes. I think the No2 type is the ideal one for shrubs, but I can't be certain. Someone else will be able to confirm that. Or, you could buy some topsoil and mix compost in with it. As long as you have a reasonable amount of soil, rather than all compost, it would be fine. Raised beds dry out more readily, so you need a bit of sustenance. 
    You'll need to top it up every so often as the level will drop too. I add spent compost [of any kind]  each year, and if anything new is planted, it gets some new compost. 
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • WildFlower_UKWildFlower_UK Posts: 236
    I know someone said to keep a few cms clear at the top, but do remember that the mixture will sink/compact slightly as it settles (particularly when it gets wet), so you may want to fill it close to the brim, then it will sink to just below the top over the comings weeks/months. Add a little less if you plan to top dress with bark or anything.
    "If you have a garden and a library, you have everything you need"
  • ElferElfer Posts: 329
    It will be a lot more economical to buy bulk bags. I needed a lot of topsoil for my lawn and give the distance bought a wheelbarrow, total was still cheaper than buying small bags and also easier to handle. The other alternative is to buy 80L bags from local soil/compost merchants, fortunately I have a local one and prices much cheaper than GC while quality is much better too. I did buy some JI no 3 and not happy with quality (some others on forum have mentioned this too) Jack's magic was much better than JO no 3.

    You also need to consider drainage in your mix but best to leave mix ratio to others who have more experience with planters than I.
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