Potassium Chlorate for Longan Trees

Longan is often dried and is also an important part of Chinese medicine.

Native to China, the Longan tree is a graceful weeping-style tree of 30 to 40 feet tall with thick leathery leaves. The tree was introduced to Florida in 1903 but did not become popular in cultivation. It is grown in Hawaii and extensively in India. Potassium chlorate has been used to encourage flowering and fruiting in this tree.

Fruit

The fruit is not as popular or tasty as the lychee, but is grown and used in much the same way. The Longan fruit is round and small, only 1/2 inch to 1 inch long. It can be creamy brown to reddish-brown with bumpy skin. The interior is whitish and soft with a strong, sweet odor. The seed is a dark brown circle that looks like an eye and has given the fruit the nickname "dragon eye."

Cultivation

The production of Longan fruit is sporadic due to unreliable flowering. Fruit can be produced in abundance one year and then sparsely for a couple of years. The harvest period coincides with typhoon season in China and hurricane season in Florida. Plantation trees are planted closely together, which also inhibits flower and fruit production. The flowers are both male and female and come in mixed panicles. There are also hermaphroditic flowers, which can function as either male or female.

Potassium Chlorate Use

Potassium chlorate is applied to the soil in Florida where warm winters have caused excess foliage formation, which impedes the flowers. The compound is also used in southeast Asian countries to promote out-of-season fruiting. Potassium chloride is a white crystalline material with no odor. It is also used in explosives and can emit toxic fumes when heated. It takes approximately two months after application for the flower production to be stimulated.

Results of Potassium Chloride

The Hawaiian Department of Agriculture conducted a study on how potassium chloride affected flower production on Longan tree. They studied 7-year-old Logan trees given applications of 250 and 500 gram treatments. The fruit set more evenly with the increase to 500 grams and had an earlier maturation. In the same trial,sodium chlorate was applied as a soil drench to another group of trees and was shown to increase flowering by 5 percent. It was not as effective in producing off season flowering as potassium chloride which improved flowering by 75 percent.

References

• Hawaiian Pacific Agriculture: Stimulating Logan Flowering in Hawaii with Potassium Chloride
• University of Florida: The Use of Potassium Chlorate and Longan Flowering Under South Florida Conditions
• Purdue Horticulture: Longan
• Sarawak Government Agricultural Research Centre: Flowering Induction of Longan Trees