Walnut, also known as walnut, belongs to Juglandaceae, and its varieties are divided into wild hickory and artificially grafted walnut. Originated in Central Asia, it is cultivated all over China. Generally, artificially improved varieties are selected because the improved varieties have higher yield and thinner shells than wild varieties, commonly known as pickled walnuts. Wild shells are thick, big and oily, and taste more fragrant, commonly known as iron walnuts. Walnut can be used as a shelter forest for road greening; Because its wood is tough and elastic, it is also the first-class material used in industry; Walnut shells can be processed into works of art, and walnuts, almonds, cashews and hazelnuts are called "four big nuts" in the international market. Walnut trees adapt to deep, loose, fertile and moist soil and cool climate and ecological environment.