How Do Trees That Produce Seedless Oranges Grow?

All plants grow from seed. Or do they? In our modern world, there are many seedless fruits and vegetables. But if they don't contain seeds, how can more seedless food producing plants grow? The story of how seedless oranges came about is an excellent example of how seedless fruits come to be---and how new seedless trees continue to appear.

Seeds are good for growing new plants, but they can be a hassle when someone's trying to eat a fruit that's full of them. We have to remove the seeds before eating, or spit them out. Neither is terribly convenient. But with seedless fruit, such as oranges, we don't need to fuss over the seeds anymore.

All seedless oranges originate from a natural mutation first discovered in 19th century Brazil, according to the website of Citrus Trees Online. The monks who cared for the tree noticed it was growing seedless oranges and soon cultivated new orange trees from the one that had naturally mutated. Not long after, according to a 1902 article in the New York Times, a seedless orange tree was brought to California and a booming seedless orange business began.

Obviously, seedless oranges can't be cultivated from seed. Instead, a method called grafting is employed to create new seedless orange trees. With this technique, a shoot or piece of new growth from an established seedless orange tree is attached to a young citrus tree of a different type. The young tree's only job is to act as a base for the shoot to grow on. The shoot is tied onto the young tree and eventually the plants grow together, creating a bump near the base of the young citrus tree. If care is taken that the young citrus tree is cut back, the shoot will grow into a mature tree, just like the tree from which it was originally cut. It will develop buds, blossoms, and fruit. The end result is a tree that produces seedless oranges.

According to Citrus Trees Online, seedless oranges can grow without seeds because the mutation "causes navel oranges to develop a second orange at the base of the original fruit, opposite the stem. The second orange develops as a sort of conjoined twin in a set of smaller segments embedded within the peel of the larger orange."

Some may wonder how the original 19th century mutation occurred in the first place. Nobody knows for sure, but according to an article in Scientific American, one of the most common reason plants stop producing seeds is a lack of pollination. This can be caused either by a genetic propensity toward difficult pollination, lack of appropriate trees to help pollinate (most fruit trees must be planted near another fruit tree of the same type in order to pollinate), or lack of interest by pollinating insects like bees.