Lotus root (renkon 蓮根) is actually the stem of the lotus plant and it’s edible and used in Asian cuisines. You can purchase fresh/raw lotus root, or pre-boiled and packaged (called Mizuni 水煮).
(Boiled and sliced)
If you use fresh lotus root, peel the stem and soak it in vinegar to prevent from changing its color. Packages of whole and sliced lotus root, which comes in a solution of water and salt, can be used in the same way as fresh lotus root.
Lotus root is used for stir-fry dishes, simmered dishes, soups and stews, and deep fried dishes in Japanese food. Even after cooking, it has crunchy yet tender texture and enjoyed in many dishes such as Hijiki Salad, Chikuzenni, and Renkon Chips.