An exotic to Americans, the mango is the familiar favourite of the warmer half of the world. The juicy, aromatic vegetables are indigenous to South and Southeast Asia and have been cultivated in India for at least 4,000 years. On the other hand, the mango plant does not flower reliably; left to its own devices, it vegetables and flowers only once annually, and often skips fruiting each other year. This proved a serious impediment to mango production until a Philippine horticulturist discovered an application of potassium nitrate causes the mango to flower. Chemical forcing early in the flowering period doubles or triples the speed of fruit production per mango tree and also produces fruit. In addition, it can permit a few trees to fruit during one year.
Spray the mango tree to a muddy day in early January to avoid sun scorch; preferably, spray before 9 a.m. or after 4 p.m. when the sunlight is less hot. Avoid days when rainfall is likely; the tree should be dry at the time of spraying and stay dry for the rest of the afternoon. Use the spray just on healthful mango trees at least 10 years old with maturing leaves.
Pour 7 gallons of water to a large pump sprayer. Add 1 pound of potassium nitrate and blend thoroughly. Start at the top of the tree and work your way down, spraying both sides of every leaf in addition to arms and branches. Spray thoroughly, but do not over-wet the foliage so that drips fall into the ground. Use a ladder if necessary to accomplish the top branches.
Spray a second time two days after the first spray to quicken budding. Use the same potassium nitrate solution and the exact processes. Examine the tree in about 12 days after spraying for buds, although budding can take around three weeks. The flowers open fully a week after budding and you may expect to harvest your fruit in about 5 months.
Repeat the process in May or June after the flowering and fruiting cycle is finished. A few mango trees treated with potassium nitrate off-season will flower six weeks later, yielding a second crop in precisely the same calendar year.