everyone else is correct, bring it outside asap. i'm not sure where you are in arizona, but you are probably close to zone 7. your tree is most likely a japanese juniper, these really prefer to be in a colder zone, but as long as you pay close attention you can make it work. you will want to check the soil several times a day. gently dig down an inch or so and if it's still moist then let it be. if it is dry, give it a good soak. as you are watering it don't worry about getting it too wet, the soil and pot are designed to not hold too much water. misting it once or twice a day is not a bad idea either. here is a good reference for general care: http://www.bonsai-bci.com/species/garden-juniper.html

Kandy, please take this as just an initial shot at attempting to find the cause of your situation: Do be aware-it is possible to overwater plants. Some of the visual cues that this is happening include chlorosis(Yellowing of foliage that is supposed to be green) wilting stems and foliage (I know-sounds wrong, but is true), other off-color effects, and lack of vigor. And yes, all of these symptoms can be caused by numerous other causal agents! Wouldn't you know it! So, it seems like you know what you're about with gardening, etc. Perhaps you can provide additional info for us. Finally, while it is too early for "fall color", some plants each year do seem to show early color change. We don't always necessarily find out the reason(s) for this effect. Are you seeing something beyond just the odd coloration here and there....to a more general. systemic situation? +oM

Can it be tap water by any chance? I used to live on the lake and used to take water from it to water my trees, but I moved and have to use tap water. I can feel chlorine smell and taste in that water.

Hey guys, I have further researched what may be wrong with my lemon tree. The last leaves that fell actually persisted a while. They were withering but still hung on to the branch for a day. My branches are dying back. I think these symptoms indicate that the tree has experienced some frost damage. Right now, it's in a really sunny spot and the weather is hot in Toronto. It is 27 degrees Celsius in Toronto and will persist about 20 degrees Celsius for the rest of the week. I also understand that I will need to prune the tree from the dead branches. I understand about the fertilizer and the Nitrogen to Phosphorus to Pottasium ratio. This is my final question. Is it safe to prune the tree now when the weather is warm or should I wait a bit longer? Anyways, thank you for your help. I am still learning how to grow and take care of my own plants and wish to become an avid gardener.