Posted: 04/05/2012 at 18:55
Where to start...
Compost which has been stored outside in the wet starts to decompose anaerobically - producing exactly the unpleasant rotted smell many have noted. It also means the compost can start to leach out compounds which are inhospitable or even toxic to plants. Compost bought early this spring may have been left over from the previous autumn and may well have been too old. If I opened a bag of compost and it smelt bad I would take it straight back and complain. No plant will thrive in it. Roots must have air - oxygen - to grow and plenty of it.
Many of the complaint posts here are about soil based and peat based composts too, such as the Levingtons and JI. Also, it's not clear that the opening question referred to a peat-free compost. Multi-purpose composts usually include peat, unless they expressly say peat-free. Many people are surprised by this - they assume that a compost which includes peat would say so clearly, but it's the other way round.
I choose not to use peat because I think it's the right thing to do - as a gardener I want to leave the world a better place, environmentally, if I can. I have grown peat-free for over 10 years and now grow 20,000 plants a year without peat. The phrase I hear murmured most often around the nursery is 'Don't the plants look healthy?'
I use New Horizon peat-free compost for pretty much everything. The retail mix is a little more fibrous than the commercial mix I now get in large bulk bags, but for three years I used the bags. I mix in a bit of horticultural grit sand to give it a bit of 'bite' for potting up. I sieve it for seeds.