Young jackfruits can have rounded or lobed leaves but when they are mature the leaves are more uniformly elongated.
When Jackfruit start to flower they are nearly always male flowers. Male flowers have thin stems while the females have stems as thick as your little finger. Male and female flowers are borne in separate flower-heads.
Male flower-heads are on new wood among the leaves or above the female. They are swollen, oblong, from an inch to four inches long and up to an inch wide at the widest part. They are pale green at first, then darken. When mature the head is covered with yellow pollen that falls rapidly after flowering.
Female heads appear on short, stout twigs that emerge from the trunk and large branches or even from the soil-covered base of very old trees. They look like the male heads but without pollen, and soon begin to swell. The stalks of both male and female flower-heads are encircled by a small green ring.
One way to increase the seed set of most fruit is to spray the very early flower bud stage and the tree in general with a solution of 1 gram of borax and 1 gram of urea in one litre of water. Say 5 to 7 litres of this solution.
Before cooking the seeds, place them on a tray in the sun and turn them occasionally. The sun will crack the hard husk so you can then remove the husk and boil the seeds for 30 minutes then salt to taste. They taste like nutty potatoes and you can also use them for nibbles. If you don’t crack the hard husk, they will explode and this is caused by water vapour trying to escape a confined space just like a roasted chestnut. You could use them as an extra to your stuffing in chicken. If you fry them after boiling, you could add a little butter, garlic salt and curry powder.
Jackfruit mature 3 to 8 months from flowering.
Picking time depends on whether the fruit will be used at home or sold.
The quantity of latex decreases as the fruit ripens. Try to cut a fruit that is green and you will have latex all over you. Cut into an over-ripe fruit and there is almost no latex. If you do get the sap on your hands you can easily get it off using lanoline soap, the kind they use in industry.
You can also make 3 shallow cuts in the fruit a few days before you plan to cut it down which will let some of the latex drain out.
Use rubber surgical gloves and coat knives with olive oil.
After ripening, they turn brown and deteriorate rather quickly. Cold storage trials indicate that ripe fruits can be kept for 3 to 6 weeks at 52° to 55° F and relative humidity of 85% to 95%.
It is normally propagated by fresh seed but you can root by cuttings as well as airlayers and grafted varieties are available. There are two main varieties. In one, the fruits have small, fibrous, soft, mushy, but very sweet carpels with a texture somewhat akin to raw oysters. The other variety is crisp and almost crunchy though not quite as sweet.
Rhizophus artocarpi attacks both the developing and ripening fruit on the tree and after harvest. Male flower clusters typically develop a fungal rot following the release of their pollen but under normal conditions this does not affect the developing fruit. Phytophthora and Fusarium are two species of fungi which can occur. Root rot is caused by an unhealthy root system.