The papaya tree (Carica papaya L.) originates from southern Mexico and Central America but can be found throughout tropical and subtropical regions. These plants live for up to 20 years and come in three types: male, female and bisexual (or hermaphrodite). You can tell the type of tree by the look of the flowers and/or fruit, although the degree of male or femaleness in a tree can shift due to changes in temperature or day length changes or the level of moisture in the soil.
Male trees have clusters of skinny, trumpet-shaped, yellow flowers. Each flower has five petals fused at the base on the end of a pendulous, 9 1/2- to 40-inch long panicle. These plants usually don't produce fruit, unless they have bisexual flower parts, which can develop a few poor-quality papayas.
Female trees have either a single or a cluster of large yellow or white flowers. These cone-shaped flowers are positioned close to the trunk, have five petals each and must be pollinated by bisexual or male flowers before fruit can develop. The round-shaped papayas on female plants are medium to large, have a visible bulge and a large cavity for holding seeds, and are of good quality.
Bisexual (or Hermaphrodite) Trees
Bisexual trees grow cylinder-shaped buds. Each has five petals partially fused at the base of a short stalk. The flowers on hermaphrodite trees can self-pollinate due to their possession of both male and female organs. Papayas on these trees resemble pears and are of good quality. They're small to medium-size, are more elongated and have a smaller seed cavity than female tree fruit.
Two main types of papayas exist: Hawaiian and Mexican. The Hawaiian type are the ones you usually find in the grocery store, because they're easier to harvest due to the low height of the plant: It rarely exceeds 8 feet tall. They have a cluster of small black seeds inside the center cavity, are pear-shaped and usually weigh no more than a pound. The flesh starts off with a bright orange or pinkish color but then turns yellow when it ripens.
Mexican papaya trees are a little easier to grow and produce much larger and heavier fruit, up to 15 inches long and 10 lbs. The flesh color ranges from pink to yellow to orange, with the fruit flavor being less sweet than its Hawaiian cousin but not lacking in flavor.
The Mexican Yellow produces medium to large, yellow-colored fruit up to 10 lbs. and has a very sweet flavor. The Mexican Red papaya is medium to very large, has a rose-colored flesh and tastes lighter than its Mexican Yellow counterpart.
Solo papayas are pear-shaped when grown on bisexual plants and round when grown on female plants. These high-quality fruits taste very sweet, weigh 1 to 2 lbs. each, and have firm, smooth skin with a reddish-orange color.