West Midlands,
United Kingdom 
Ericaceous compost - adding lime.
I have been unhappy with many potting composts this year. I have ended up using a good quality ericaceous compost to which I have added garden lime at the advised rate of about 500g per 100L.
The plants seem happy enough but is there anything else different about commercial ericaeous compost other than leaving out the lime? Higher peat content of course, but anything else?
24 Aug, 2013
Not really, all of them are based on a high percentage of sphagnum peat, usually with a small percentage of bark fines, sand and nutrients which will include potassium nitrate, sulphate of ammonia and, if you're lucky, some trace elements. John Innes ericaceous, though, is virtually all loam with feed added and therefore peat free.
27 Aug, 2013