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“First, sieve your compost”

  • “First, sieve your compost”
  • “First, sieve your compost”

Over the years I have tried just about every type of compost available, from John Innes (very nice but prohibitively expensive) through home-made (not the best of textures, and sadly full of weed seeds) ending at Super-Cheap Multi-Purpose. This is not for putting on the garden, I hasten to add, but for plant sales - as well as gardening, I sell plants, obviously, and I have found it safer to use bought-in compost, with no chance of bugs or diseases to distress the customers (that means YOU!). I use whatever I can get most cheaply, so that generally means the “sheds” and the largest bag that I can handle.

I am regularly horrified at the quantity of contaminants, so, as an experiment, when I opened a new bag recently, I kept them all. The bag concerned was, as you can see from the pictures above, a big 145 litre bag from B&Q, in their own-brand Verve range.

In case you are wondering how I found the contaminants, they popped up when I was sieving it – what? Don't you sieve your compost? You don’t? But you should try it! For three reasons, quite apart from it being so good for the stomach muscles…

Firstly, the resultant compost is much finer and nicer in texture.

Secondly, the “nuts” left over from sieving are excellent for top-dressing the pots - the lumpy texture prevents a crust forming, reduces evaporation, and is easily replaced if surface weeds or those damned liverworts (you might remember that I’ve been invaded by Marchantia for the past two seasons, and they are driving me mad) take over the top layer.

And finally, it allows me to take out all these hand-hurting contaminants so that I can use it barehanded, which is much preferable for potting up.

When I finally emptied the bag, I put the collection of bits on an A4 sheet of paper and took a photo, which you can see above.

How amazing is that lot?

Any number of “bits of plastic”: thin bin-liner plastic in many colours; rigid bits in clear, black, and blue; some strange nylon woolly stuff; a good collection of small rocks and pebbles; one large piece of hard plastic; quite a few largish bits of woody stuff which clearly slipped through their grid, and two bits of glass, one of which was bigger than my thumbnail but was mercifully rounded.

I have found there is nearly always some glass in multi-purpose compost - in fact, I think that’s why I started sieving in the first place, as I draw the line at contributing my own blood to the plants.

So there you have it – three perfectly good reasons to sieve your compost, and at the same time, How To Get A Beautiful Nice Compost At The Minimum Price!

Comments (9)

  1. Grower

    Jeremy Wright

    In any other product 'foreign articles' in the mix would be good cause to complain to the manufacturer. However, with compost it is at least reliable sign that you are using recycled green waste, which is good, and not destroying the natural environment by using peat.

    I spent an interesting afternoon a year or so ago with Chris Field, MD of Field Compost (how could he resist with a name like that!), a small family run compost manufacturer in Suffolk. He showed me how green waste comes into the plant and the different stages of sieving the product goes through with increasingly finer meshes, until it is ready for bagging and distribution.

    Field Compost pride themselves on going the extra mile with sieving (or 'screening' as they call it) so the product you get is finer and there are hardly any foreign items. I have had several cubic metres of their Field No. 1 soil improver which is screened to less than 10mm and it is gorgeous soft, dark, wonderfully smelling stuff. The plants in my garden love it.

    Rachel, you can probably work out by measuring the average diameter of the particles what screen mesh Verve go down to. With particles that large and especially if there is glass, it makes good sense to do a last sieve yourself. But with a product like the one from Field Compost, there's not really a need.

  2. Grower

    Rachel the Gardener

    Hi Jeremy,

    I have been on tours of all three recycling plants near where I live - green waste, kitchen waste, and landfill - which were organised by the local council: they were all very interesting, in very different ways! If anyone wants to know more about what happens to our waste, and how an anaerobic digester works, do please feel free to have a look at my blog, And do contact your local councils and ask if they run tours: most of them do, and it's a fascinating day out.

    I also spent a day with Melcourt Industries,, who make the most perfect rolls eyes in heavenly bliss compost, Silvamix is their brand name (they screen to 6mm, actually!) and it's peat-free, but unlike many of the substitutes, it is easy to "wet" and lovely to handle. It's a bit too expensive for me to use on a daily basis, and I was very sad when my free sample bag was finally all gone.

    However, all is not lost - at least sieving the cheap stuff gives me some exercise!

  3. Grower

    Winifred Field

    Thankyou for your discussion, if nothing else it makes me smile. It seems impossible to get good compost which will be the same quality next season too.
    I don't know that my old arms would cope with sifting, but I'd love the stomach muscles! As you and others say the best seems to be too expensive for us gardeners on a budget, and it's not readily available anyway, I've not come across Fields or Silvamix, even though my surname is Field.

  4. Grower

    Good Earth Gardens

    I've just spent a morning digging out a couple of compost bays which have kitchen waste as well as garden clippings and the biggest bugbear is the straggly pieces of 'biodegradable' plastic in the mix which I keep having to pull out and then put back in for more composting. I haven't been sieving this compost as I'm using it as a mulch so I figure there's no need, but it's worrying the amount of glass there was in that bag of yours...!

  5. Grower

    Rachel the Gardener

    Winifred, I make my sieving easier on my not-as-young-as-they-were arms by using a circular sieve - you can buy modern plastic versions which are much lighter than the old-fashioned metal ones - and only filling it part full before I shake, shake, shake. I find with multi-purpose compost that you have to manually squash the bigger lumps anyway, so I am not doing any one motion for any length of time.

    My actual process, in case you are interested, is to collect a bucketfull of compost from the bag (and when I say "bucket" I mean one of those black plastic pots they display cut flowers in, at supermarkets) then sieve it in three installments into my potting tray. I then slosh in some water and dampen it, using exactly the same motion that my granny taught me to rub up pastry - I'm sure you know the one I mean! By doing it in small installments, nothing gets too strained.

    I find the Verve stuff is extremely variable, sometimes it is like dust and sieves straight through with just the contaminants left on the grid, and sometimes it is damp and heavy and needs a lot of shaking or rubbing.

    My dream is to have one of those free-standing sieves with a handle which you turn!

    GoodEarthLady, I know exactly what you mean about so-called biodegradeable bags!! I am always writing on my blog about the difference between compostable and biodegradeable: in fact, I'm actually writing a book on the subject of Compost and Leaf Mould at this very moment - well not at this VERY moment, obviously!

  6. Grower

    Winifred Field

    Last week "Verve "was suggested as a suitable peat free compost in a reply to a letter in "Garden News", perhaps you should send them a copy of your photo with all its "extras".

  7. Grower

    Rachel the Gardener

    Hahaha! Good idea - and while I'm at it, I'll point out that you'd have to buy the one that is specifically labelled "peat free" - most of their composts, especially the cheaper ones, are most certainly not peat free.

    In fact, I was highly amused a couple of years ago to see a "shed" offering "reduced peat" compost - but nowhere did it say what proportion of it was peat, nor what proportion the "normal" compost contained - what a useless statement!

  8. Grower

    BR2 Agapanthus and More

    Back in the day, when 'Focus' was one of the sheds, their peat-free was truly diabolical and put me off for life - it was a grey colour liked incinerated something or other. I believe (reading Garden) that things may have improved.... but the problem is that no-ones compost is consistent year-on-year.

    As for brand I'm not too concerned as historically I created my own mix with inexpensive compost plus hort. perlte plus sharp sand and long-term (18m) fertiliser. Used to sell masses through Country Markets (when it was W I Markets), now only sell bits from the house and donate a few crates of plants to local Hospicecare every May.

  9. Grower

    Rachel the Gardener

    Oh, Focus, I remember them!!

    Yes, a lot of the early "peat-free" stuff was truly horrible, and I am sure that it contributed to much of the resistance to going peat-free.

    I agree completely with you about the lack of consistency within a brand, it's very annoying. That's why I'm not loyal to any brand at all, I go for whatever is cheapest! I find that once it is sieved, they all become much of a muchness, anyway. I, too, make up my own "mix" to suit whatever I am potting up or potting on.

    It would be nice to think that spring might be here soon - it's currently too blustery to go outside!

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