What does it mean that old trees and green vines open new flowers?

This sentence actually means that people, things or things are full of vitality again. The literal meaning of "an old tree opens a green vine" is that an old tree opens new flowers. Although it is an old theme, it still refers to life with a new angle. Although no longer young, but full of vitality. So it is a more auspicious meaning.

The old man is not old at heart;

Life, from youth to youth, and then to eighty. High-spirited, ambitious and powerless, we are not only extravagant in age, but also in health.

In fact, there is nothing to sigh about when people are old. We should keep a young heart. As long as the heart is young, people will not be "old". The old is the body, the young is the soul, and it is the heart that will always be curious and innovative about the unknown world.