How to grow Longan

Where to plant

Longans crop most reliably where fall and winter are cool, below about 59°F, but frost free and fairly dry, followed by a warm spring and hot summer. Warm, rainy winters push leafy growth instead of flowers, and heavy rain at bloom knocks off flowers.

Plant in full sun in the warmest part of the garden that does not flood. Longans tolerate dry soil but not wet: young trees can die after 5 to 10 days of flooding in hot weather. They are not salt tolerant. Young trees are damaged at 29 to 31°F and may be killed at 26 to 28°F, so they are slightly less cold hardy than lychee.

• South Florida and Hawaii: grow outdoors.
• Central Florida: possible in the warmest, most protected spots; protect young trees from frost.
• Elsewhere: longan needs a frost-free site and is not practical outdoors.

Choosing a variety

'Kohala' is the main longan grown in Florida, and UF/IFAS reports that nothing superior has yet been identified. Buy an air-layered or grafted tree of a named variety; seedlings do not come true, bear late and often give poor fruit.

How to plant

1. Choose a healthy tree, usually in a 3-gallon pot, that is not root bound.
2. Clear a ring of grass 3 to 10 feet across. Dig a hole 3 to 4 times wider and 3 times deeper than the pot. No compost or fertilizer is needed in the hole.
3. Set the tree so the top of the root ball is level with or slightly above the soil, backfill with native soil and water well. Where the water table is high, plant on a mound 2 to 3 feet high.
4. Mulch 2 to 6 inches deep, keeping mulch 8 to 12 inches from the trunk.

Watering and feeding

Water young trees regularly. Once trees bear, water regularly from flowering through harvest. Reducing water from late summer through winter slows leafy growth and helps flowering the next spring. Avoid lawn sprinklers on timers near the tree, which overwater it.

A month after planting, give about 1/4 pound of a young tree fertilizer with minor elements, repeating every 6 to 8 weeks in the first year and increasing gradually as the tree grows. Mature trees get 2 to 3 feeds a year, around bloom and harvest. On alkaline soils, longans need iron chelate.

Pruning and care through the year

• Prune a few small and medium limbs each year to keep the tree about 10 to 15 feet high, which makes picking easier and reduces hurricane damage.
• Thin heavy fruit set in spring: when fruit are 1/4 to 1/2 inch across, cut off one half to two-thirds of the end of each large cluster. Removing about half the fruit greatly increases fruit size.
• Keep grass away from the trunk and avoid heavy lawn fertilizer near the roots, which can reduce fruiting.

Harvesting

In South Florida longans are picked from mid-July to early September, mostly in August. Ripe fruit turns an intense tan, but taste is the real test, as fruit does not get sweeter after picking. Cut whole clusters with about a foot of branch.

Put picked fruit in the shade and cool it quickly. Longans keep 5 to 7 days in plastic bags in the refrigerator and freeze well whole.

Propagation and saving seed

Air layering is the usual method in Florida, best from April to August; roots form in 10 to 12 weeks. Longans can also be grafted onto seedling rootstocks.