Kentucky may not be a tropical state, but you can still enjoy a citrus tree as one of your plant friends.
Citrus trees enjoy well-drained, slightly acidic soil. They should be watered as the top layer of soil begins to dry and can be fertilized sparingly during the summer months when they show some new growth.
While your tree is inside during the winter, give it as much sunlight as you can and check the leaves regularly for any signs of pests like aphids, mites, or mealy. Water when the top layer of soil starts to dry out, but be sure that your tree is planted in a pot with good drainage--citrus trees don't like to grow in a bog.
Bring your tree outside during the summer so that it can enjoy the balmy temperatures. Give it a transition period in a shady area before moving it into full sun; otherwise, you could shock the tree and fry the foliage. Transition the tree back into a shaded location toward the end of the summer so that it adjusts more easily to going back inside.
A Few Caveats
Even with good care, citrus trees are unlikely to produce bumper crops of fruit in our climate. You may occasionally get a small fruit from your tree to enjoy. This doesn't necessarily mean that your plant is receiving bad care: Kentucky just doesn't get enough heat or sunlight year-round to support abundant fruit growth.
Citrus trees can also look a little scraggly during the winter months when the amount of available sunlight decreases. Decrease your watering so the plant doesn't get overwhelmed, and resist the urge to fertilize during seasons of slower growth. Your plant will bounce back when the summer temps and sunny days return.