First off, you won't really be growing jackfruit indoors. For the indoor gardener, the jackfruit falls into the same category as mango, papaya, and avocado. They are definitely a novelty, and in their native habitat, they grow to large, columnar trees up to 70 feet in height. They are lovely trees, with large, oval leaves and straight, regal trunks. The real interest, though, comes from their fruit.
The jackfruit is one the world's most magnificent fruit: a single mature fruit can weigh up to 40 pounds. Shaped like an enormous kidney bean, they have pebbled and rough green skin, and their flavor is indescribable. They are sweet and mild and best served cold. Indoors, clearly, most people won't have room to let a jackfruit grow to maturity and fruit--it can take up to 14 years for a jackfruit to set fruit. Still, if you somehow get access to jackfruit seeds, go ahead and sprout them and see what happens. The very worst thing that can happen is you'll have an interesting conversation piece.
- Light: Jackfruit seeds can be sprouted in the spring and immediately exposed to dappled sunlight. They prefer strong light while growing, so move them into a sunny window or outside on a patio deck. They are highly susceptible to cold weather, especially early in their lives, and cannot tolerate frost or freezing weather.
- Water: As tropical plants, they require a steady supply of ample moisture. Keep them continuous moist throughout the year, including the winter. Jackfruit do not have a natural winter dormancy, so it's best to keep their growing conditions warm, bright and humid all year if at all possible.
- Fertilizer: Feed weekly with a weak liquid fertilizer. They are not particularly heavy feeders, but especially seedlings and younger plants thrive with regular applications of fertilizer.
- Soil: A light, fast-draining potting soil is perfect. You can use fortified soils.
Jackfruit seeds are viable for about a month after harvesting. Jackfruit seedlings are quite sensitive and do not like to be disturbed if at all possible. As a result, it's best to sprout them in a somewhat larger pot and avoid the early transplanting that many plants require. To increase the odds of germination, soak the seedling overnight, then plant into a sterile seedling soil and keep it warm. Expect germination is about two months, although it may happen somewhat faster. Jackfruit can also be propagated by air layering, although this is a somewhat more advanced technique that requires access to an adult plant and several months.
Jackfruit have a long and delicate tap root, which makes repotting difficult. It's best to avoid repotting young jackfruit if it's not necessary, so ideally you can grow them in the same pot you sprouted them in for the first season. Assuming your plant makes it through the winter, you can repot in the spring again, stepping up one or two pot sizes.
When repotting, be careful not to disturb the roots of young plants.
Jackfruit belong to the Artocarpus family, or the same family as the breadfruit made famous by Captain Bligh. The main species is the A. heterophylla. According to Purdue University, the origin of the jackfruit isn't known--the plants are widely distributed throughout tropical Asia and India, where they have been in cultivation for hundreds of years. Because they are a commercially important plant, jackfruit have been extensively hybridized over the years. Growers have worked to encourage traits like early fruiting, late-season fruiting, large fruit, small fruit, and sweeter fruit.
Jackfruit are tropical plants and act like it. They are not really viable outside below about zone 10, and they really require lots of water, sunlight, humidity and warmth to thrive. They cannot tolerate frost or extended periods of drought. Under good conditions, young trees grow quickly, and if you manage to survive the winters, you could have a nice-sized foyer tree within a few years. If you're very lucky, your tree might even make it to setting fruit. Fruit are typically harvested within 8 months of flowering and can be harvested when green (and treated like plantains or breadfruit) or when they are fully ripe. Young jackfruit trees are susceptible to mealybugs and aphids.