Groundwort, also known as[1] Screwgourd, is the tuber of the caddisfly of the family Lamiaceae, a perennial herb. The flesh of the tuber is crisp and tender, and can be made into preserves, sauces, and pickled products, which are very delicious. When eaten, it is mainly eaten cold, and can also be processed into pickles, canned vegetables, sweet fruits, etc. It is one of the famous "eight treasure dishes" and "assorted vegetables" at home and abroad. Yangzhou canned screw vegetables are the top pickles. Chongqing calls it "Digun Niu", and southern Shaanxi calls it "Diyuer" (sound).

Screwcarp is a perennial herb. There are stolons underground. When mature, the top swells into a spiral fleshy tuber. The stem is upright, 30 to 120 cm high, square, with opposite leaves, ovate to oblong-ovate, and covered with short bristles on both sides. Blooming in summer, the flowers are lip-shaped, light purple, in whorled inflorescences; the corolla is about 1.2 cm long, with hair rings inside the tube, the upper lip is upright, the lower lip is three-lobed, and the middle lobe is nearly round. Nutlets are oval, with small tubercles. It likes growing in warm and humid lands or near water.

It is wild or cultivated in various parts of my country. It is rare in western Beijing and mostly in Hebei and other places bordering western Beijing.

Dihuan is usually made into pickles, which are very crisp and delicious, and are a good dish to go with rice. Many Korean residents use it to make pickles.