In-situ stewed walnut is a unique walnut skin color (i.e., shade skin) formed after a certain period of growth in natural environment due to various natural reasons. Usually black and red, uneven skin color. Different shades of skin color are the characteristics of naturally stewed walnuts. Walnut with green skin falls to the ground and then goes down the mountain. During this period, different parts of the green tangerine peel were hit to different degrees, and the degree of damage was also different, so the decay time of the green tangerine peel in the future was different. Dew and rain in the wild are also influencing factors. For example, if the green husk undergoes a rain in the process of decay, the shadow before the rain will be darker than the shadow after the rain.