|MadSci Network: Botany|
Pineapples are native to South America. About the only place you will find a pineapple with viable seeds is in South America on a naturally growing pineapple plant. A pineapple develops from multiple flowers. There are many thick, hard floral bracts or leaf-like petals on the outside of a pineapple. If you did find a pineapple with seeds, it would contain one seed for each flower that produced the pineapple.
It is difficult to find seeds in commercially grown pineapples. Commercial pineapples have been selected for their vestigial seeds (the same is true for bananas). Commercial pineapples are propagated by planting a vegetative part of the plant (the stalk, the tufts at the top of the fruit or the tufts at the bottom of the fruit). They are not grown from seeds.
Admin note: David Hershey adds the following:
Pineapples are pollinated by hummingbirds and are self-sterile, meaning they cannot produce seeds if they pollinate themselves (self-pollination). To get seeds, pineapples must be cross-pollinated. Cross pollination is prevented in two ways. First, the importation of hummingbirds is banned in Hawaii where many pineapples are grown commercially. Second, all the pineapples in one field are genetically the same, so that if pollen is transferred from one plant to another, it is still self-pollination. Cross pollination requires that the plant providing the pollen is genetically different from the plant receiving the pollen. Cultivated pineapples would produce seeds if they were cross-pollinated. However, a seedy pineapple fruit would be very undesirable because it would contain hundreds of hard seeds so growers make sure that they are not cross-pollinated. Collins (1960) says eating a seedy pineapple is like eating a normal pineapple containing a thousand tiny bits of gravel.
Pineapple fruit development is an example of parthenocarpy or development of fruits without seeds. In nature, this may be an advantage to the pineapple in two ways. First, the leafy crown at the top of a pineapple fruit can root and produce another plant, so even without seeds a pineapple fruit can reproduce the plant. Second, a seedless fruit may provide food for the animals that normally disseminate the seeds. This could prevent the animals from starving or migrating in years when few flowers are successfully cross-pollinated and seeds produced. Also, the seedless fruit of the pineapple makes it a very desirable food for people so we grow thousands of acres of pineapples. Many of our most popular fruits are seedless, such as bananas, seedless grapes, naval oranges, seedless grapefruit, seedless watermelon and certain types of figs and persimmons.
Samson, J.A. 1986. Tropical Fruits. New York: Longman.
Collins, J.C. 1960. The Pineapple. New York: Interscience.
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