Standing beside an old sau (dracontomelon) tree on Tran Hung Dao Street, Nguyen Van Hung raises his eyes to the canopy, looking for the elusive sau fruits.
In a few seconds, Hung's four limbs skillfully sliver and slide up the tree's trunk, and in less than one minute, the 20-year-old disappears into the greenery a dozen meters in the air.
On the ground, another youth passes Hung a long bamboo pole with a hook. After a rustling in the branches above, a cascade of green fruit drops to the ground. Hung's friend collects the fallen sau fruits in a plastic basket, leaving the dead branches and leaves in a mess on the pavement.
The young men spend 20 minutes on each tree along the street. They've got to move quickly as other groups of boys are right behind them, scouring the city for what's left of the fruit.
Hands and chest smeared with the tree's resin, Hung, who wears no safety equipment, said he's never fallen out of a tree.
"If I had, I wouldn't be here."
Last month, Hung and his peers left their hometowns in the north-central province of Thanh Hoa to become "freelance" sau harvesters in Hanoi, a profession that has been illegal for years.
But ever since the French planted the sau trees along the old city's streets, Hanoians and Vietnamese across the country have been hungry for their fruit.
The booty for a group like Hung's usually weighs in at 30-40kg per day. But if they're extra lucky, they can haul in 100 kilograms from a single outing. For every kilogram sold, they earn VND25,000 (US$1.2). They can charge higher than market prices as the fruits harvested directly from Hanoi's trees are considered fresher, healthier and more sour than those grown in gardens or on farms.
The Hanoi Green Trees Park Company had once tried to auction the rights to harvest sau, but no one signed up.
These days, alongside groups of youths like Hung and Co., a few old people can be found picking one fruit at a time with long bamboo poles.
The elderly poachers are tolerated, even though picking the fruits is illegal, because they don't damage the trees or make a mess.
But people caught picking dracontomelon the way Hung does are often fined and ordered to clean the area. They have their poles and baskets confiscated, but that has not stopped this hundred-year-old tradition.
BOX: Sau (Dracontomelon duperreanum) is a genus of flowering plants which produces white flowers of fresh fragrance and an edible green fruit that is eaten in Cambodia, Vietnam and China. In Vietnam, the plant is called cay sau and is a common urban tree in Hanoi. A drink made from sau and jasmine water is a tasty treat enjoyed by locals.
Sau season lasts from June to September in Hanoi. The fruit is made into several dishes and drinks with sugar, chili salt and ginger.
It can be cooked with sour soup or eaten fresh with fish sauce mixed with sugar and chili. Some people prefer it plain in a cold beverage with sugar. The most popular dishes of sau are sugared, salted, dry sau, called o mai.
Hanoi's late writer Bang Son had commented that Hanoians love the fruit to the extent that their blood has the taste of sau.