Transcript:
Violet and Charlie Brown are standing in the field next to a tree. He points at the tree and says,"This, Violet, is an oak tree..."
He points to another tree and continues,"And this is a birch tree...."
Violet points in front of her and asks,"What kind is that one?" He looks in the direction she's pointing and says,"That one? That must be a bamboo tree"
They stand in front of a flag placed in the seventh hole on the golf-green. She says,"It certainly grows straight, doesn't it?"
Original comic:
I seem to remember that this concept is recycled in a later strip, but with Lucy misinforming Linus.
I found this strip on https://peanuts-search.com/, seems to be what you're thinking of?
Yes, that's the one!