Hi all,
It shouldn't really matter what the name is, what you want is a "control released fertiliser". If the Miracle-gro is the
"all purpose continuous release plant food" (little brown capsules in a plastic jar) it should be OK, but I would expect it to leach nutrients (including NH3) more rapidly than Osmocote.
Miracle-gro belongs to Scotts, Osmocote was developed by Sierra, subsequently bought by Scotts and now is owned by ICL (whoever they may be). Fisons produced a similar product, "Ficote", now possibly available as "Nutricote", this doesn't contain any NH3 nitrogen, so would be a safer product for us, but I'm not sure about its availability in the UK.
cheers Darrel