The leaves of the mustard plant are long and green, and are known as the "longevity vegetable," while the name for turnips (caitou) is homophonous. with "good omen," so both these veggies are auspicious.
芥菜的葉子形狀修長翠綠，而有「長命菜」之稱，白蘿蔔又叫菜頭，諧音「彩頭」，都是吉祥象徵。