Seedling trees may take five to eight years to grow fruit. Seedling mango trees grow much bigger and stronger than the nursery trees and have an indestructible root system. The seed needs to come from what is called a "polyembryonic" variety. What that means is that the seed will sprout several identical trees. And those seedling trees will be identical to the parent tree. They are clones, the fruit you harvest will taste the same.