Where is a pear flower crushing begonia?

"Pear tree hits begonia" is a joke in Su Shi's poem "Playing Zhang Xian".

Around the year 1070, Zhang Sanying, Su Shi's good friend and "Neng Shi Hui Yue Fu", married a new concubine. This year, Zhang Xian was just 80 years old, and this newly recruited concubine was only 18 years old. Su Shi was deeply impressed by his friend Zhang Xian's "old cows eat young grass", so he recited a poem: eighteen brides and eighty lang, with white hair and red makeup. Two nights of mandarin duck quilt, pear tree pressing begonia.

Zhang Xian, an 80-year-old man with white hair, married a beautiful girl 18 years old, so Su Shi took the opportunity to make fun of Zhang Xian's wedding night. Pear trees press Haitang, which refers to a white-haired husband, and Haitang refers to a young woman with a good face.

Extended data:

Su Dongpo (1037 ~11) and Zhang Xian (990~ 1078) were both poets in the Song Dynasty, and Su Dongpo was famous. By contrast, Zhang Xian's popularity is almost zero. However, in the field of Ci, Zhang Xian is a person with personality, a romantic temperament and an immortal. His ci works mainly reflect the life of literati and the love between men and women, and are the representatives of Huajian Ci School in the Northern Song Dynasty.

Zhang Xian is more than 40 years older than Su Dongpo, but because they both love poetry, they become friends and often sing poetry together.