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!