What do you mean, "Plums are yellow and sunny, and streams are full of mountains"?

It means: when plums are yellow, it is sunny every day. Take a boat along the stream, reach the end of the stream, and then take the mountain road to continue.

From the famous "Trilogy Knife Bell" in Song Dynasty.

Plum yellow, sunny,

The stream dries up, but it swims in the mountains.

The shade does not reduce the road,

Add oriole four or five times.

Full text translation:

When plums are ripe, it is sunny every day. Take a boat to the end of the stream, and then take the mountain road. The ancient trees on the mountain road are green, which is not inferior to the scenery on the water road. There are a few orioles singing in the depths of the forest, which adds a bit of interest.

Once upon a time (j:) (1084-1166), the word Jifu, magistrate, self-named Chashan lay, posthumous title Wenqing. Poets in Southern Song Dynasty.