In the Song Dynasty in China, an artist called Wen Tong was especially fond of drawing bamboos. He planted a lot of bamboos in his garden so that he could observe the process of their growth and appearance in different seasons. He knew bamboos so well that whenever he took up the paintbrush he already had a picture in is mind, and thus he could always paint bamboos in a vivid and lively way.

This idiom is used to indicate having a well thought out plan ready before one sets out to do something, making success assured.