Rare. Walnuts are both two-sided, and the three-sided and four-sided walnuts are genetically mutated. Because the mutation rate of the four-sided walnut is higher than that of the three-sided walnut, the three-sided walnut is rarer, so the four-sided walnut is cheaper. Wenwan Walnut is a kind of walnut with collectible value, which is formed by the special selection and processing of walnuts. Wenwan Walnut originated from the Han and Sui Dynasties, was popular in the Tang and Song Dynasties, and prevailed in the Ming and Qing Dynasties. Because of its unique shape, it has medical value and artistic value, and then has collection value. Wenwan Walnut mainly includes three types: Juglans regia, Juglans mandshurica and Juglans regia, while Juglans mandshurica includes Juglans regia, Juglans mandshurica, Juglans mandshurica (four famous kernels) and Juglans regia.