Papaya are not a natural houseplant—which is precisely why you might consider growing them. That, and because the seeds are so plentiful and easy to sprout, they are basically free. A single supermarket papaya will yield several hundred black seeds. Simply dry them out on a paper towel and you'll have enough seeds to sprout papaya for the rest of your life. The plants themselves are beautiful and highly tropical.
Papaya feature wide, deeply lobed leaves atop a fleshy trunk. Papaya is a very fast-growing plant, and in nature, it quickly assumes its adult size and bears fruit. Indoors, it won't be practical to grow a 15' tall papaya all the way to fruiting (and unless you had both male and female plants, it wouldn't be fertilized so there'd be no fruit anyway). But that doesn't mean you shouldn't grow these fantastical plants. It just means you won't be eating them.
- Light: Full sun, or as bright as you can provide. Papaya are also a great patio plant for summer climates and will grow very fast.
- Water: Prodigiously. As the plant grows, expect to water daily.
- Temperature: On the warm side (up to 80˚F). If you keep the plant during winter, try to keep the temperature as warm as possible, with high ambient humidity.
- Soil: A loose, well drained, very rich potting mix.
- Fertilizer: Fertilize abundantly. Papayas are very rapidly growing herbaceous plants that consume fertilizer.
By seed. Papaya sprout readily from seed, even the seed harvested from grocery store papaya. To prepare seeds, scoop them from a papaya and spread them out on a single sheet of paper towel and leave out to dry for a week. At the end of the week, roll the seeds around to remove the dried husks of the seed coverings, then store them in a cool, dry place.
To sprout papaya seeds, place them in seedling starting soil and keep moist and warm. Seeds sprout quickly and the plants will begin rapid growth.
Papaya grown from seed should only be repotted once: from the container you started the seed in into a larger permanent container. Unless you live in USDA zone 9b or higher, your papaya is a single-season novelty plant. It's best to grow them in fairly large containers (at least 3 gallons) as part of a mixed container. At the end of the season, cut the papaya off at the soil level and let the other plants fill in. If you live in a warm enough climate (no frost), you might be able to transplant the papaya outside.
Papaya have been in cultivation for so long that the origins of the commonly cultivated plant (Carica papaya) have been lost. It's believed the plant probably originated in Central America, but it's now found in every tropical country in the world, where it's an important food source. As a landscape plant, papaya is often grown as a tender annual in colder climates, and as a houseplant, it's grown only during warm months in large containers. There are several varieties of papaya available, based on their fruit type, but this is immaterial for indoor cultivation.
Just use seeds from whatever fruit are available.
Papaya grow in similar situations to bananas, requiring bright light, humidity, heat, plenty of fertilizer and water. Also like the banana, it's an extremely fast-growing semi-woody plant with large leaves that are the very essence of the tropics. As the plant grows, the lower leaves will yellow and fall off, leaving behind half-moon shaped leaf scars. It's unlikely an indoor papaya will flower, but if it does, you'll find out if your plant is male or female. Female plants have fragrant white flowers that emerge from the axis between the stem and leaf axis. Male plants have smaller yellow or white flowers that grow on pendant stalks. Papaya sap can be slightly caustic, so it's best to avoid the sticky white sap whenever possible.
The plant itself is not toxic, but it is used as a digestive aid because of the presence of enzymes that help digest protein.