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Compost, talk to me.

So further to the Red Currant thread (and the planter thread) I’m also going to be growing kiwi in a pot (as a climber up the house).

Obviously im going to need to fill the planters and pots with a suitable medium (about 300l worth...). Now the sods I cut from the lawn last year to make the veggie patch are still rotting down and the compost bin isn’t far enough along to provide sufficent compost  and at present I can’t harvest much from other parts of the garden (although it is a nice sandy loam)

 Both the red currants and kiwi recommend a well draining compost like a John Innes no.3 however this is obviously an expensive option. 

Can I get away with a mix of some No.3 and the rest cheap generic 3 x 50l bags for £10 type stuff? Or dig a percentage of the loam out of the veggie batch and replace with cheap co post? 

Thanks in advance



  • pansyfacepansyface PEAK DISTRICT DerbyshirePosts: 21,225



    WHY NOT?


    Apophthegm -  a big word for a small thought.
  • ObelixxObelixx Vendée, Western FrancePosts: 28,564

    Commercial composts such as John Innes no 3 are made to a set formula for nutrients and texture and are sterilised so have no pathogens.   The same goes for the Levington formulae for ericaceous composts.  If you want tasty fruit you have to feed the plants and provide a decent medium for their roots to grow well in order to pass the nutrients to the plant above.

    People who've been gardening for years and have long established compost heaps can get away with using their own but usually mix it with some loam or grit or sand or moisture retentive houmous material depending on the needs of the plants they're growing.    If your own compost heap is small/young/cold it will not provide such good quality growing medium and is best used as a soil conditioner on garden beds.

    In any case, commercial composts have enough nutrients for 90 to 100 days so you'll need to add some slow release fertiliser and occasional liquid feeds of tomato fertiliser for flowering and fruiting plants to thrive.  If the plant is to stay in the pot for several years you need to scrape away the top inch or two of compost every spring and add fresh along with slow release food every spring and the regular liquid feeds.

    Plants are living organisms and worth the time and care to grow well.   Give them the right conditions and they grow strong and sturdy and make you happy.  Skimp, starve or mistreat them and, at the very least, they will sulk and fail to thrive.

    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • Pete.8Pete.8 Billericay, EssexPosts: 9,865

    The bagged 50L composts will not last more than a year or so two.
    They break-down and turn into sludge after a couple of years. They're not designed for long-term planting. Just for raising seed,cuttings etc.
    If you need a long-term potting compost you're best sticking with John Innes - it's not a brand, it's just a recipe.
    The ingredients are listed here

    It'll be a lot cheaper to mix you own rather than buy in bags - if you can get hold of loam (which is composted turves)

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • Im not really looking to cut corners, however 300l + of ready mixed No.3 isn't cheap!

    I have pretty good soil, there's a good 500-600mm of rich sandy loam overlying sand on to weathered sandstone so the soil its self is pretty sandy. 90 years ago before the house was built it was all farm land so it's not bad. 

    I was more wondering if buying bagged name brand No.3 was essential  or whether it was something I could approximate in the garden with a mix of some garden derived Loan, some bought in generic compost and some No.3 / other components. My compost bin has only been going since last summer so it's a bit young to be 

  • (Apologies hit submit mid typing) 

    ...supplying me with well totted organic material to mix in yet. 

  • Pete.8Pete.8 Billericay, EssexPosts: 9,865

    If it were me, I think I'd use a mix of good topsoil (from your garden or bought), horticultural grit (20%), peat (15-20%) and well rotted manure (15%) available in 50L bags

    PS - I should add that I've never grown Kiwi, so don't know what sort of compost they like, but the mix above should suit most non-acid loving plants

    Last edited: 17 February 2018 09:00:29

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • ObelixxObelixx Vendée, Western FrancePosts: 28,564

    Not sure you can get peat anymore so look for coir which is sustainable.

    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • the budget compost are all peat.  Wilco do one for £3 and lidl sometimes have them. 

  • PalaisglidePalaisglide Posts: 3,414

    We always mixed our own formula of John Innes but we always steamed the soil first, we had our own steamer system and it did about half a bucket at a time so we started buying it. If you put the Fruit into the ground then you would mix some compost and grit with the soil first, a pot is a different thing altogether. The soil will be in the pot until you repot, It will be in the pot for some time until you repot which is often years so why not start properly with the correct mix, the yield will repay the cost many times over.

    I agree with everything Obelixx said above and fruit is hungry you will need to feed from spring to fruiting at least every two weeks, buy or use cheap you get cheap so I would use the best after all it will be a one off until you repot and then the plant will be mature, you could mix your own.


  • BorderlineBorderline Posts: 4,687

    If you say you have the soil you believe is loam and free draining, you should use that. John Innes 3 is not really necessary, just because you have a raised bed or planter etc. The main bit is to incorporate rotted compost at least once a year and feed your plants if necessary. The approach should be, put your plants in and see how they grow and react to the conditions if you are unsure. Over feeding and mixing short cut routes like peat is not really necessary. It may turn out, your garden soil is just enough when mixed with rotted compost, so whether it is cheaper or mid-range, I think you should use your soil if you have it and mix with compost first. 

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