Saikan no sanyu (the three friends of winter) (歳寒三友)

"Saikan no sanyu" were the popular subjects of bunjinga, the literati paintings that first appeared in the Sung period (China)
It designates specifically three subjects that are a pine tree, a bamboo and a Japanese plum tree. The three subjects are often painted all together but also could be individually represented by choice. In Japan, it is called 'shochikubai' (pine, bamboo and plum trees).

Pine trees and bamboos keep their green even in winter, and plum trees bloom in winter. These were regarded as the symbols of 'incorruption and constancy,' representing the ideal of litterateur. In Japan, it was introduced in the Heian period and became popular among the common people after the Edo period. However, the 'shochikubai' is regarded as the symbol of 'auspicious' things that is different from the original idea of China.

As for the beginning, it is considered that in the Sung period in China, Chinese authors Wen Tong, Su Shih and others painted bamboos as the subject of ink-wash paintings and expanded the subjects to plum trees, orchards, chrysanthemums and pine trees afterwards. Among them, three subjects that were the pine tree, the bamboo and the plum tree became especially popular because of the above reason. In the Yuan and the Ming Dynasty, they also became popular as the subjects painted on ceramic wares. In Japan, they are mostly painted in ceramics, lacquerwares, and dyeings and weavings.
Also, they became a part of life among common people as the subjects used with Kadomatsu (New Year's pine decoration), Hina dolls, and on celebratory occasions such as a wedding or a childbirth, and they could be combined with the subjects such as 'cranes and turtles.'

[Original Japanese]