Peonies were called 花王 or 百花の王, "the king of flowers," in China long before the title crossed to Japan along with the plant itself — a status still reflected in the flower's Japanese associations with nobility and composure rather than simple prettiness.
By the old calendar's own logic, once the peonies scatter, spring itself is considered over — this is the final kō of 穀雨, and of spring's six sekki altogether. The next kō opens 立夏, the beginning of summer.
What's blooming as 牡丹 is specifically the tree peony, a woody shrub — not the same plant as 芍薬 (shakuyaku), the herbaceous garden peony that blooms just afterward and is often mistaken for the same flower. One common explanation for 牡丹's own kanji ties to this: 牡 (male) reflects an old, since-corrected belief that the plant propagated only from root cuttings rather than seed, and so lacked anything read as a "female" reproductive stage in classical botanical thinking, while 丹 (deep red or cinnabar) names the color of the original wild species before centuries of cultivation produced today's wider range.
The season's earliest, smallest ayu, appearing well before the fish reaches the size more associated with summer — delicate enough to eat whole, bones and all.
Literally "summer mikan," despite actually being eaten now, at spring's own close — a naming mismatch that, fittingly, lands on the exact kō marking the old calendar's handoff from spring to summer.
Thinner-skinned and more tender than the burdock sold later in the year, needing less of the usual scrubbing and soaking before cooking.
Eaten pod and all while still flat and immature — left much longer on the vine and it becomes a very different vegetable.
The two flowers look similar enough to be routinely confused, but the plants themselves aren't close: botan is a woody shrub that keeps its stems through winter, while shakuyaku dies back to the ground each year like a perennial herb — a distinction summed up in an old expression describing an elegant woman as standing like a shakuyaku, sitting like a botan, and walking like a lily, using each flower's actual growth habit as the shape of the compliment.
Several temples and gardens hold festivals timed specifically to this brief bloom window rather than a looser flower-viewing season — Nara's Hase-dera and Tokyo's Ueno Tōshō-gū peony garden are among the most visited. It's a narrower, more deliberate tradition than cherry-blossom hanami: built around one flower's short peak rather than a whole season's general mood.
"Standing, a shakuyaku; seated, a botan; walking, a lily" — A long-standing description of an elegant woman, documented in Edo-period sources from the 1770s–90s though its original author is unknown — each flower's actual silhouette supplies the comparison: shakuyaku's tall, upright stem for standing, botan's fuller, lower shrub-form for sitting, and the lily's graceful sway for walking.
牡丹 is read botan in Japanese but is a direct borrowing of the Chinese name for the plant, unlike many native Japanese flower names — a small trace of how thoroughly the flower, and the reverence attached to it, arrived from the continent as a single cultural package rather than being independently discovered and named in Japan.
Daikonshima, a small island connected to Matsue by causeway, produces roughly 90% of Japan's cultivated peonies despite the island's name literally meaning "daikon radish island" — cultivation there began around 300 years ago and now exports as far as the Netherlands, the US, and Taiwan.
Unlike cherry blossoms, peonies hold their bloom for a genuinely short window — worth checking a specific garden's timing rather than assuming any spring visit will catch them.
Buson's haiku found its subject in the flower already loosening, not at its freshest — a fully open bloom a day or two in often has more to look at than a bud just opening.
"The peony scatters — two or three petals fall, layering over each other."
Fully open blooms cut and brought inside tend to shatter within a day or two — buds just beginning to loosen last considerably longer in a vase.
By the old calendar's own accounting this is the last kō before summer begins — a natural point to finish, rather than merely continue, whatever felt like "spring's business" this year.
Buson chose to write about the peony not in full bloom but in the act of falling apart — two or three petals, already settling on top of each other, still fresh enough to hold their color and shape even as the flower itself is finished. It takes a specific kind of attention to notice something at exactly that point, past its peak but not yet faded. What have you only really seen clearly once it was already ending?