The reasons for the focus on spring and autumn, Shirane suggests, derived partly from their importance in the farming cycle, and partly from the influence of China. By the eighth century, “a larger grammar of seasonal poetry” began to emerge, according to which emotions were not expressed directly, but implied through seasonal references instead. This required a sophisticated understanding of their usage and became what we think of now as Japan’s traditional poetic art.
Speaking of which, how about some seasonal haiku from the Japanese masters?
Bashō:
A crow
has settled on a bare branch—
autumn evening.
Buson:
Autumn evening—
there’s joy also
in loneliness.
Issa:
The holes in the wall
play the flute
this autumn evening.