How to make mango bloom flowers to produce off-season fruits

Mango is regarded as the national fruit of the Philippines. (u_e5c/Pixabay)


The mango is one of the most important fruit crops in the Philippines. In fact, it is regarded as our national fruit. Beloved by Filipinos, mango trees are usually planted in the backyard of households for their shade and fruits that are enjoyed eaten ripe or unripe. The fruits are also processed into dried mango fruit, jams, and flavoring to ice creams and other sweet delicacies.

Mango is the 8th most produced fruit in the world. The largest producers of mango are India (42%), China (10%), Thailand (7%), Indonesia (5%), and Mexico (4%). The Philippines ranked 9th among the top exporting countries, contributing 2% to the world in terms of production output, and carabao mango is the third most exported fruit crop in the Philippines, next to banana and pineapple. However, only less than 5% of the total production is produced for export.

Mango is naturally a highly seasonal crop that usually bears fruit from May to June. However, with the discovery of flower induction practices or the application of certain chemicals to initiate flower development, the mango fruit is now available year-round.

Traditional Philippine practices

If you grew up in the province of the Philippines, you may remember your parents or neighbors burning swept leaves, twigs, and branches of plants under the mango tree. This is called siga or smudging. This is done not only to incinerate trash, but folks also believe that doing this will make the mango tree bear flowers. The practice of smudging for the tree to bloom is somewhat true as the ethylene, a gas present in smoke, has been scientifically proven to induce flowering in some crops. However, this method is unreliable because the tree cannot be totally covered in smoke. It is also laborious, hazardous, and may cause pollution in the environment.

The law now prohibits smudging under the Ecological Solid Waste Management Act or R.A. 9003 and the R.A. 8749 or the Clean Air Act. Any person who violates the law will be punished with a fine of not less than P2,000 but not more than P10,000 and imprisonment of not less than three days but to not more than 30 days.

Another traditional practice to encourage mango trees to flower and bear more fruit is hacking the tree trunk using a bolo. This practice may be similar to the effect of girdling or removal of a strip of bark tissue that is usually done in apples, grapes, oranges, olives, and peaches to improve their fruit sets. Although it is effective in some crops, hacking tree trunks is a destructive process, which is why it is not widely practiced commercially.

The discovery of chemical flower induction in mango

In 1969, Philippine national scientist Dr. Ramon Barba discovered the use of potassium nitrate (KNO3) for flower induction of mango. The mango crop was once disregarded and hardly utilized, only serving as a source of shade and backyard crop. However, with the application of this technology, the mango industry experienced a sudden surge in growth and success. After the full adoption of this practice in 1980, Philippine mango production tripled. Now, mango is the number one fruit crop in terms of the value of production next to banana and pineapple.

His discovery revolutionized the mango industry in the Philippines and globally. The discovery of potassium nitrate to induce flowering in mango has become a worldwide practice. Mexico, the current number one exporter of mango globally, has used this technology since 1975.

Application of potassium nitrate

For effective flower induction, before applying the potassium nitrate to the mango tree, make sure that the tree has mature dark leaves, at least four to five month-old stems, and a rest period of seven to eight months after the last fruiting season. Also, ensure that there should be no expected rainfall within the next few days.

In applying potassium nitrate, mix four kilos per 200 liters of water. Spray the solution on the branches and leaves until totally wet. Alternatively, calcium nitrate can also be used instead of potassium nitrate. In this case, mix five kilos of calcium nitrate with 200 liters of water.

Spraying should be done when the leaves are dry in the morning from sunrise until 9 AM or late in the afternoon, starting at 4 PM, to prevent leaf burn because of exposure to sunlight.

Spraying can be repeated after two days to hasten the effect. After 14 days, expect the emergence of flowers.

Flower induction is usually done during the regular season of November to February, where the expected months of the harvest are from March to June. For off-season production, flower induction is performed from March to October, and harvesting is expected from July to February.


Even though potassium nitrate is considered a beneficial chemical in agriculture, it can also be used as an ingredient in manufacturing explosives. Hence, the importation, sale, and possession of this chemical, including the alternatives such as calcium nitrate, ammonium nitrate, sodium nitrate, ammonium sulfate, and potassium sulfate, are restricted and strictly supervised by the Firearms and Explosives Office (FEO) of the Philippine National Police (PNP).

Under the Republic Act 9516, only licensed mango contractors authorized by Fertilizer and Pesticide Authority (FPA) can secure a permit from PNP-FEO to purchase, sell, and distribute potassium nitrate and the other mentioned alternative chemicals. All growers and mango contractors without FPA licenses are not allowed to use potassium nitrate and other nitrates. However, they can still use commercially formulated flower inducers. Furthermore, agro-pesticide dealers are also prohibited from selling these chemicals.

Artificial flower induction is now one of the essential crop management practices in commercial mango farming. The discovery of potassium nitrate as a chemical for flower induction has transformed the global mango industry. Not only has it increased the production of mangoes, but it also created more opportunities for processing and by-product making.

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