Is it possible to grow tropical fruit plants indoors in the Canadian winter?

Citrus needs full spectrum light and citrus fertilizers to thrive. Since your plants are young, they are tender and need specialized TLC. You need to keep them warm: Hang a bare light bulb close to the soil to warm it. They need full spectrum color waves for at least 8 hours a day. You can purchase a full spectrum light bulb from Home Depot or Lowe's and put it on a timer. They need humidity which can be accomplished by placing the pots into a pan with stones. Water only from the bottom to help the roots reach and grow. Use a half strength water soluble fertilizer until the trees are freely leafing and branching. Then switch to a specialized granular citrus fertilizer. Be very careful not to overwater and don't pinch off or cut anything until the trunk of the trees are at least the thickness of a pencil!! The tender shoots may not be able to handle the stress..