This is Rick Heflebower, Horticulture Extension Agent for Utah State University located in Washington County.
I would like to give you a few tips today on growing citrus. A lot of times when Thanksgiving comes, or the first week of December, I often get phone calls from people wanting to grow citrus. These would be trees like lemons, limes, and navel oranges.
These can be a bit challenging to grow, but it is doable in Utah, provided you are willing to bring them in during the wintertime. So usually by December, even down in the St. George area, we're starting to have freezing temperatures at night. These types of trees cannot withstand temperatures below about 32 degrees. They'll sustain enough damage that the plant will be severely damaged, or it may completely die.
So when selecting what to plant, the best thing to do is to grow dwarf varieties of citrus and put them in a planter that they can be picked up and moved indoors during the wintertime. And then, when you do have them indoors, select a sunny location. A minimum of six hours of sunlight doesn't have to be direct, but it should be a well-lit area. Use a good grade of potting soil and when you water them, make sure that you keep them moist but not overly wet.
Another tip would be to fertilize them about every three months, even though they're indoors with something like a 14:7:7 fertilizer with a 2:1:1 ratio of nitrogen, phosphorus, and potassium.
Well, I hope this was helpful to you as you consider possibly growing some citrus trees in the Utah area.