I get asked this question many times, the only answer I can give you is what I do, summer two or three times a week, winter once a week or longer, its a very difficult question and will also depend on your own growing environment. They should be watered frequently and not be allowed to fully dry out, it also depends on the time of year and the ambient temperatures. A good observation will be if the frequency is correct or requires modification a clear sign is a loss of foliage (leaf drop) would indicate irrigation problems, too much or too little.