According to Wu Jun, a litterateur in the Southern Dynasties, the custom of climbing mountains and enjoying the moon on the Double Ninth Festival originated from the legend of "avoiding scenery" in the Han Dynasty. According to legend, during the Eastern Han Dynasty, Runan people worshipped the immortal Fei Changfang as their teacher. Fei Changfang once told Huan Jing that there was a disaster on the ninth day of September and told him to go home as soon as possible. He told his family to sew some bags, put dogwood on them, tie them on their arms, and then go up the mountain to drink chrysanthemum wine to avoid the disaster.

On the ninth day of September, Huan Jing took the whole family to climb the mountain according to Master's words. Sure enough, it's safe. When I got home at night, I found that all the chickens, dogs, cattle and sheep were dead. Since then, people climb mountains, have picnics, wear dogwood and drink chrysanthemum wine every September 9 to avoid disasters. Although this is an absurd story, it reflects the psychology of our ancestors.

The ancients thought that "nine is Lao Yang, and the anode must change". Count from one to nine, and Yang counts to the end. If you count further, you have to start from the beginning. This is the so-called "anode will change", so nine is a very profitable and unfavorable number, and the number from prosperity to decline implies ominous factors. On the ninth day of September, the two numbers of "Lao Yang" overlap, which is even more unlucky. Therefore, people need to find a solution. The solution is to climb the mountain and insert dogwood.

This understanding is actually a reflection of the idealistic world outlook of Yin and Yang, but it has caused the folk custom of climbing mountains and inserting dogwood on the Double Ninth Festival, which is very understandable in ancient times when science was underdeveloped.

In later generations, people climb mountains no longer to avoid or ward off evil spirits, but mostly for enjoyment. On the day of Double Ninth Festival, the sky is crisp, the mountains are red, the forests are dyed, and the rivers are clear. It is the best time to climb high and look far.

The so-called mountaineering is mainly mountaineering, and some people climb stairs.

The custom of wearing dogwood was gradually changed to inserting dogwood in the Tang and Song Dynasties, so there is a sentence in Wang Wei's poem, "I know my brother climbs but one of them is less." There was also the custom of rewarding ministers with dogwood in the Tang Dynasty.

Conclusion: Cornus officinalis belongs to Anisodaceae, and its stems and leaves can be used as medicine. It is said to have the effect of avoiding epidemic. It can be seen that it is really good to insert Evodia rutaecarpa on the ninth day of September, regardless of the saying of avoiding evil spirits. Perhaps prolonging life and preventing plague are the real reasons why the ancients wore dogwood.