In Lang Son, black grass jelly - also known locally as tien nhan dong, suong sao, luong phan thao or tien thao - is a familiar crop cultivated by residents in communes of the former Trang Dinh district such as Doan Ket, Cao Minh, Tan Tien, Kim Dong and De Tham.

According to traditional Eastern medicine, black grass jelly is believed to help detoxify and cool the body, while supporting treatment for conditions such as nephritis, acute arthritis, colds, diabetes and high blood pressure.

Beyond its medicinal uses, the plant is also a key ingredient in a number of local dishes.

Nguyen Nhung, owner of a black grass jelly production facility in Trang Dinh commune, Lang Son province, said the crop grows quickly and can be harvested after around four months.

Farmers typically harvest two crops a year - the summer-autumn season in July and August, and the winter-spring season in November and December. However, locals only harvest the plant when the top leaves begin to curl, before flowering starts.

“When harvesting black grass jelly plants, people cut them close to the roots, then spread them out in the yard to dry under the sun for a day before covering them with tarps and fermenting them in piles for one to two days.

Once the leaves turn black, they are dried under the sun for another one to two days until fully dehydrated, then stored for later use.

This process helps preserve the quality of dried black grass jelly plants, ensuring the best raw ingredients for producing ready-to-eat jelly and powdered jelly,” Nhung explained.

According to the producer, dried black grass jelly plants can be used to make refreshing beverages or a variety of traditional dishes.

The most popular product is ready-to-eat black grass jelly, favored by both locals and tourists for its cooling taste and perceived health benefits.

Nhung said making black grass jelly requires both experience and meticulous preparation.

First, the dried plants are washed several times before being simmered in water for four to five hours until softened. The liquid is then extracted and carefully filtered to obtain pure black grass jelly essence.

The filtered extract is cooked again with additives such as sugar, rice flour or tapioca starch and water in suitable proportions - typically 70-80% jelly extract and 20-30% additives, mixed with 15-20 liters of water.

The mixture is continuously stirred over heat until it thickens into a smooth consistency and takes on an amber-brown hue under light.

“If the ratio between jelly extract and additives is properly balanced, the jelly will set firmly while remaining chewy, crunchy and elastic, with minimal water separation and a distinctive aroma,” the vendor added.

Once cooked, the jelly is poured into small trays or containers to cool before being sealed and refrigerated.

Nhung noted that Trang Dinh black grass jelly is sold not only locally but also shipped to distant cities and provinces to satisfy growing demand for regional specialties.

Trang Dinh black grass jelly is packaged in round paper boxes or plastic containers weighing between 400 grams and 1 kilogram, priced at around VND45,000 ($1.73) per kilogram.

Having tasted black grass jelly in Lang Son several times, Huyen Trang from Hanoi said she was impressed by the dessert’s chewy texture and refreshing flavor.

“I’ve tried black grass jelly from Tuyen Quang and Cao Bang, and they were quite good, but personally I find Trang Dinh black grass jelly the most delicious.

It has a cooling taste, chewy texture and a distinctive fragrance. It’s delicious on its own or combined with coconut milk, tofu pudding, sweet soups or milk tea,” Trang shared.

The Hanoi resident said she occasionally orders around 10 boxes of black grass jelly from Trang Dinh to Hanoi, both for her family and as gifts for friends and relatives.

“Although the distance is quite far, transportation is convenient now. Delivery only takes four to five hours, and the jelly still arrives in good condition thanks to careful packaging and transport,” she said.

Trang also noted that besides helping cool the body, black grass jelly is often enjoyed as a low-calorie snack that may help curb cravings during weight loss.

“If you want to lose weight, you can order a version with less sugar. It still tastes great without making you worry about gaining weight.

Whenever I crave snacks, I simply cut up some black grass jelly and add a little coconut milk. It’s also suitable for both children and older people,” she added.

Thao Trinh