Inducing Mango Bloom with Potassium Nitrate Sprays
Getting a mango tree to produce fruit requires flowers first, and many trees bloom only every other year. A spray of potassium nitrate can prompt annual flowering. This guide explains dosage, timing, and application for home growers in warm climates.
By Elliot Brooks5 steps
Home growers who plant mango trees (Mangifera indica) hoping for a long annual harvest of smooth, sweet fruit run into several hurdles. One is that mangoes grow only in the mild climates of USDA hardiness zones 11 and 12. Another is that the trees must flower before they can fruit, and they usually bloom just in alternate years. Applying potassium nitrate, however, can encourage them to blossom every year. The Filipino horticulturalist Dr. Ramon Barba is credited with refining this technique in the 1970s, according to the World Intellectual Property Organization.
Forcing mango trees to flower and fruit more than once a year lowers their total yearly yield over time.
Step 1
Spray dry trees when no rain is forecast for at least six hours after you finish. Cloudy weather is best; if that isn't possible, treat the trees before 9 a.m. or between 4 and 5 p.m. Direct sunlight can burn mango foliage that has been sprayed with potassium nitrate.
Step 2
Mix a potassium nitrate solution at the right strength. A low dose of 1 to 2.5 percent suits healthy, large, mature mango trees with mature leaves and buds, applied seven to nine months after the last harvest. For younger trees whose leaves and buds are just beginning to mature, or for mature trees harvested within the past six to seven months, use a 3 to 4 percent solution. To work out how much powder you need, multiply 128 (the number of ounces in 1 gallon) by the chosen percentage. A 2.5 percent solution calls for about 3.2 ounces, or 6.4 tablespoons, of potassium nitrate per gallon of water.
Step 3
Fill your spray tank with enough water to treat your mango trees. Add 1/4 to 1/2 ounce of a spreading-sticking agent, or the amount the manufacturer recommends, per 10 gallons of water, and agitate thoroughly. Then add the suitable amount of potassium nitrate powder and agitate again.
Step 4
Spray each tree until the solution thoroughly coats its branches and leaves, but not so heavily that it drips. Agitate the mixture often so the sticker and powder stay dispersed. If a tree is too large for you to reach every branch, use a ladder braced against the trunk to reach the canopy. Start with the highest branches and work downward, coating each area well before moving on.
Step 5
Watch for flower buds, which should appear 10 days to two weeks after spraying. If needed, protect the opening flowers from insects or fungal attack by spraying with ready-to-use organic neem oil. At the first sign of a problem, coat all plant surfaces until they drip. Repeat every one to two weeks until the pests or the disease-favoring conditions have gone.
