With a rough appearance and an itch-inducing nature, củ nưa - a root vegetable also known as konjac or khoai nưa - is dubbed a culinary gem "from beneath the earth," found from northern to southern Vietnam.

The nưa plant, part of the Araceae family, grows naturally in provinces such as Son La, Cao Bang, and Ha Giang. All parts of the plant, including leaves, stems, and especially the tuber, are used in food and medicine.

Thanks to its economic value, nưa is now cultivated in places like Hue, Hai Lang (Quang Tri), and Tra Cu (Tra Vinh) primarily for harvesting its tubers.

Le Thang, a grower in Hai Lang, Quang Tri, shared that nưa is typically harvested from September to November, depending on the local climate and soil.

“Farmers watch the leaves. When most turn yellow, it's time to harvest. Tubers collected before full maturity are softer and less itchy when eaten,” he explained.

He advised harvesting on dry days to avoid damaging the tuber, which can lead to rot. Any bruised or cut tubers must be separated and stored carefully.

After harvest, the roots are cleaned, peeled, and reveal a yellowish flesh. If not used immediately, they should be stored in a dry place for longer shelf life.

Depending on need, the tubers may be sliced, sun-dried or oven-dried and ground into flour - or cooked fresh into items like cakes, tofu, or noodles.

“Nưa flour is finer than tapioca, with more starch. It’s commonly used in puddings, noodles, vermicelli, and cakes. These products are increasingly popular,” Thang added.

To prepare, the tubers are washed, peeled, then soaked in rice water or salted alum water to remove the itchiness. After soaking for 1–2 hours, they're rinsed and ready to cook.

The simplest dish is boiled nưa, which preserves its soft, fluffy texture and neutral flavor. Boiling for 20–30 minutes removes its itchiness, and a pinch of salt can enhance the taste.

More elaborate dishes include nưa cake. The fresh root is blended with a bit of water until thick, poured into molds, and steamed for 30 minutes. In some variations, the root is pre-boiled, blended with seasoning, and allowed to set before steaming - yielding a dessert with the soft, cool texture of jelly.

In addition to boiling or making cakes, nưa can also be cooked, battered, and deep-fried for a unique, crispy treat.

“The root has little smell or taste, so it’s often eaten with sugar or salt. It’s chewy, soft, and low in nutrition but rich in starch, making it a very filling food,” Thang noted.

According to the book Vietnamese Medicinal Plants and Remedies by Prof. Dr. Do Tat Loi, the raw root contains toxins that can be neutralized by cooking with lime. It can also be crushed into a poultice for skin irritations, boils, or snake bites.

Beyond its culinary uses, nưa has long held a place in traditional medicine, documented in classical works like Compendium of Materia Medica and Lei Huo Ji.

Thao Trinh