The Da River, or Black River, forms the border between Dien Bien and Lai Chau provinces in Vietnam's Northwest, or Tay Bac. The river's banks are home to people of the Thai ethnic minority group, who cultivate rice and orchards, raise livestock and fish. As well as supplying fish and watering their fields, the Da River and surrounding streams supply the Thai with a special type of aquatic plant, which they harvest from underwater rocks at year's end and in early spring. At this time, the water weed is at its thickest, growing at about a meter below the water's surface.

This plant is usually harvested by women, who roll up their skirts and wade in waist-deep. To cut the plants they bend low in the water typically removing their tops to avoid soaking them. Harvesting these plants gives the women a chance to bathe naked, an act that has a special name in the Thai language ? ai em. They store the collected plants in a xoong, a woven bamboo basket with wide mesh that is placed in the river, thereby allowing water to circulate to keep the contents fresh. When the baskets are full, the women stand up, roll down their skirts and return home with their precious greens.

After being thoroughly rubbed clean, the plants are ready to be used in a wide variety of local dishes. The plant is typically grilled with basil, citronella, ginger, garlic and onion, as well as mac khen, a type of jungle pepper that grows in northwest Vietnam. This pepper supplies the dish with a distinctive flavor. Before being grilled, the plant is kneaded into small balls and placed in a clamp. These balls are then grilled over charcoal for about 20 minutes. The balls may also be wrapped in banana leaves before grilling, or baked in coals.

As well as eating this plant fresh, Thai people also dry it in the sun. It is also added to grilled fish and meat dishes. Sticky rice is steamed in a type of basket called a com khau, then covered with the grilled water plant and stuffed with meat or fish. Bite into one of these sticky rice balls and you can taste the simple perfection of traditional Thai cuisine. A small glass of homemade rice wine complements the dish's flavors.

Should you travel to ethnic Thai villages around Son La or Dien Bien, be sure to seek out a meal made with this river plant. Sample this local specialty and you'll get a taste of the Thai people's rich and gracious culture.