What do you mean, the leaves fell to the ground, that is, the day we met?

Wait until autumn, that's when we meet.

Leaves fall to the ground, usually in autumn. Only in autumn will the leaves begin to wither. Therefore, this sentence is to wait until autumn, that is, when we meet.

Because the temperature in autumn and winter is generally low and the climate is dry, it is easy to lack water, the plant growth stops, all the leaves fall off, and the tender leaves grow again in the next year.