QuestionWhat is the ratio of cow manure to potting soil in 12 inch clay pots?
AnswerUse 1 part Cow Manure to 4 parts soil.
The manure MUST be aged. Use un-aged manure and you'll wipe out your Roses overnight with that stuff.
A year is the usual rule.
12 inch pots are a little small for Roses. I hope you're growing Miniatures.
Thanks for writing.