All hokku are seasonal hokku, being written and marked (as practiced today) with one of the four seasons. That comes from hokku having originated in a temperate climate. In other climates this may vary to a summer season, a rainy season, and a winter season; to a spring, summer, and fall without winter; or to even just a dry season and a wet season.
I am in a temperate zone with a climate similar to that of Japan (and of Britain), so hokku as I teach it has four seasons. Those individuals living in areas with fewer seasons should adapt their hokku to those areas.
Because hokku is seasonal verse, we write according to the present season, and not only that, we read hokku according to the season as well. That is to keep us in harmony with Nature. Occasionally we will use out-of-season verses for learning, but in doing so we must remember that these are exceptions to the standard practice when writing and reading.
But on to summer hokku. We cannot fully understand the aesthetics behind summer hokku without a knowledge of the two elements of Yin and Yang that comprise the universe. These are qualities that are opposite, but which combine and work in contrary harmony throughout all things.
Yin is cold, silent, motionless, wet, dark, passive.
Yang is warm, noisy, moving, dry, bright, and active.
The entire year is a cycle of change from Yin to Yang and back again:
Winter is deepest Yin. When Yin reaches its maximum it begins to turn to Yang. As Yang grows, winter changes to spring. As the Yang of spring grows further, it changes to summer, and finally it reaches a point of maximum Yang — the height of summer, at which it begins to change to Yin. As Yin grows, summer fades into autumn (fall), and as Yin grows even more as Yang declines, autumn dissolves into Winter, and Yin grows to its maximum until the cycle repeats.
The same cycle happens in a day. The middle of night is Yin, which begins to change to Yang. Dawn is a mixture of Yin and Yang, and Yang grows until midday, when it reaches its maximum and begins to decline into afternoon as Yin increases, then evening, then night again.
This is the cycle too of life, including human life. Birth is comparable to the beginning of spring; youth is the height of spring, which fades into the summer of maturity; then comes the decline into autumn, which is like the late afternoon of the day. And then come evening and night, old age and death.
One will see these cycles repeated again and again in hokku, and when we know their correspondences, we will begin to grasp an important part of the aesthetics of the hokku.
Summer, then, is a season when Yang grows gradually to its height before beginning its decline into autumn. In the first part of summer, Yin declines as Yang increases. In the second part, Yin grows as Yang begins its decline.
The most obvious characteristics of summer then, are the Yang characteristics of heat and dryness. This is just the opposite of the Yin characteristics — cold and dampness — of winter. So we can say that both summer and winter are the “extreme” seasons, while both spring and summer are the “balanced” seasons in which both Yin and Yang work out their proportions without extremes.
That was a rather long but essential introduction. But knowing all that, we now know that because summer is one of the “extreme” seasons, its hokku are likely to often be characterized by opposites. That is why Yin qualities are frequently so important in summer hokku. It is Yin that brings out the “extreme” character of the season. So we only realize fully the importance of water (Yin) on the hottest and driest days of summer. The same may be said of the coolness (Yin) of a breeze on a blazing hot summer day. And there are further interesting but opposing combinations of the two, for example the sweltering heat (Yang) of a summer night (Yin).
It is important in discussing these combinations and permutations to realize that the balances and proportions of Yin and Yang are constantly changing and are not absolutes. There are Yin elements to be found even in the height of summer, and we often take advantage of these to set off the intensity of the Yang elements of heat and light and dryness.
I recall when in my college days an instructor asked us all a question about how one character in a play acted as a “foil” to another. It quickly became obvious that none of us knew what he meant by that, assuming mistakenly that he meant a “foil” in the sense of a fencing sword. But the use of the term originates in a time when thin, bright metal foil was placed behind an inferior gemstone in a setting to enhance its brightness and make it stand out. One thing being a “foil” to another, then, means one thing emphasizes the qualities of another, makes another stand out more strongly. That is how we use Yin as a foil to the Yang of summer:
They have rolled
Out from the leafy shade–
The hot melons.
Kyorai wrote that. We can see it does what we have just talked about; it combines the Yin of the shade and leaves and the watery melons with the heat characteristic of summer. We feel the heat even more, seeing the Yin, watery melons that have grown hot in the intense sunlight, and the leafy shade from which they have rolled.
There is also another way of emphasing the heat — by “pouring it on,” that is, by increasing the extreme of heat by using something that is in harmony with, rather than contrasting with it. This is using harmony of “like” things rather than harmony of contrasting things. Hyōka wrote:
There’s a wife
And children in my house;
The activity and wants and chatter of the children, the wife with her remarks and tasks and complaints, all combine in the hot little house to make the heat even more intense for the man, who feels that if he were alone, things would somehow seem cooler. It is this sense of “crowding” when one wants space and coolness that is in harmony with the heat of summer. That is why, for example, a mass of buzzing flies on a hot day would also be in harmony with the summer heat, making it even more irritating.
An extreme may be found even in the intense light of summer, as in this verse by Kyorai:
Stones and trees
Are glaring bright —
That reminds me of a beach I once visited in the height of summer, and the light reflected off water and sand was so intense one had to squint.
Summer, then, gives us an opportunity to work with extremes, with Yang modified only slightly to greatly by the addition of this or that Yin element. That does not, however, mean that all summer hokku must be harsh. Summer has its harshness, but its pleasantness also.
Here is a summer verse by Kitō which nonetheless is heavy with Yin:
The clear water.
Looking into the flowing clear water on a summer’s day, we see the tiny fish, tails wriggling, being pulled slowly downstream in the current up which they are facing. The predominant element here is the Yin of the water, but we feel the summer in its clearness and in the wriggling of the fish.
Summer too has its more “Yin” days and its more “Yang” days. Everything is relative, and it is the wonderful changes wrought by these differences in proportion that make things all the more interesting.
And so we return to our original premise: All hokku are seasonal hokku. At base, each verse is about a season. So summer hokku should express the summer in some way. And they should do it through sensation, through touching, tasting, hearing, smelling, and seeing.
We must remember always to keep our hokku simple, our sensations direct. Deal in real things, with water and stones and wind and flies and leaves; omit thoughts and abstractions and commentary, and do not try to write “poems.” Instead, our goal in hokku is to express the season through sensation — through sensory experience — and if we succeed in doing that, the poetry will take place inside us, instead of on the page.
That is how hokku works.