Dear Laura: Orange trees will begin to flower and set fruit on their own schedule, that can be anywhere from 5 years on up. Be sure the plants get plenty of sunshine so there is enough food for the plant to grow, flower and set a crop of oranges. If the plants have been fed lots of nitrogen fertilizer, then they will have lots of leaves and no flowers. Hold off on using high nitrogen fertilizers until the plant slows down vegetative growth and then it will begin to think about producing flowers and fruit.
Sincerely, Rihard Hentschel