A kigo (季語, "season word") is a seasonal reference found in Japanese poetry. Often consisting of a single word but also sometimes a phrase, a kigo is many times drawn from the natural world, but might also refer to a human activity. A kigo implies a season of the year. For instance, if the reference is to cherry blossoms, it is understood that the season of Spring is implied. One of the most common kigo is in fact sakura, the Japanese word for cherry blossom. It is actually so common to refer to cherry blossoms that often the generic Japanese word for blossom, hana, is taken by itself to refer specifically to cherry blossoms in a Japanese poem such as a haiku. Traditional Japanese haiku generally contain a kigo as a matter of form. There are in fact large compilations of kigo called saijiki which contain notes on different specific kigo, as well as example poems.
With a kigo, a word or phrase quickly brings to mind not just a thing, but also a time for that thing or activity. For example, "sunbathing" is a kigo that is associated with the Summer season. The poet doesn't have to also separately note to the audience that the poem is set within the summer months. He has already conveyed this by the activity described in the poem. If a poet refers to sunbathing then it is also understood that he is referring to Summer. Likewise, wisteria are associated with summer, as are iris and lotus. Apples and persimmons find a home in Autumn. So do some pears.
I wonder, as we compose our tasting notes full of fruit descriptors, if we have thought beyond the flavors to the seasons that they imply?
A monk sips morning tea,
the chrysanthemum's flowering.
Matsuo Basho as translated by Robert Hass