The 5th lunar month is marked as "Poison" month in Chinese Farmer's Calendar. This is because the gem, insect, fly, mosquito, and pest are active in this summer month and people is easy to catch infectious disease. On the Dragon Boat Day, Chinese put the leaves of Acorus and Artemisia on the doors or windows to repel insect, fly, flea and moth away from the house. Those leaves have anti-poison function and can prevent an epidemic.

The leaves of Acorus are linear, sword-like, glossy, evergreen and lush. Artemisia belongs to daisy family with fern-like leaves.

In Tan Dynasty (618-907 A.D.), Rebel Huang scouted the target village and prepared the next attack in 5th lunar month. He saw a woman carrying a boy in her one arm and holding the another boy's hand was running. Rebel Huang asked her why running. She said, "We heard Bandit Huang is coming, we need to run for our lives." Huang asked again, "Why carrying one in the arm, but holding another with hand?". The woman said, "The one in the arm is the only son of my husband's elder brother. The other one is my son. In case, I cannot run quickly enough, I will drop my son and save my husband brother son." Rebel Huang was very touching, then told her that "Go home quickly and put Acorus and Artemisia on your door, then rebel forces won't hurt your family." She returned to the village and told some people. On the 5th day of 5th lunar month, Rebel Huang's forces entered the village, all the families with Acorus and Artemisia on the door were safe. The custom keeps since then.