I know its an old post, but since I live in Ontario I thought I would give my two cents. I find the easiest part of growing citrus in Ontario is the actual growing, the hard part is getting the right amount of chill hours at the right time. My orange tree grew fantastic for about 10 after I bought it and then it started to bloom in October! Which I think threw it out of whack, and put a lot of stress on it. Other than my orange I keep all of my citrus in my basement under lights(I use compact fluorescence which work well enough) until the beginning of March and then they go out to my hobby greenhouse, until May and then they enjoy the nice summer sun. One thing I can't stress enough is to use fans to make the branches strong for when you move them out in the summer, and to use CHC mixes instead of regular potting soil(which wisdom I owe to the people on this forum). One last thing I find it incredibly difficult to find citrus in Ontario, I have been to Humber which has a nice selection and Colasanti's near Chatham which also has a nice selection ( 1-2 gallon plants for about $30-$40 best price I have found. Another good place near you mintchris is Bradford greenhouses(but only in Spring and summer). Most of my citrus is from seed which I have collected from fruits or I have received generously from members at this forum. I wish you good luck with growing citrus in Ontario.