A little research shows that chrysanthemums have been cultivated in Japan since the Nara Period (8th century) and were especially popular in the Edo Period (early 17th to late 19th century). In fact, the Imperial Seal of Japan is a chrysanthemum and is used by the Emperor and the members of the Imperial Family.
The exhibition nearby has its roots in the Edo Period and apparently made the city quite famous. The exhibitions used to include shaped shrubbery as well as famous scenes, historical figures, and dolls all decked out in chrysanthemum finery. Sadly, those days are mostly gone since few people have the time and skill to produce these labour intensive pieces. However, much smaller versions are exhibited every year to give a taste of once was, and every year I look forward to seeing what will be on display.
The chrysanthemum exhibition just ended last weekend but here are links to 2 blog posts that include pictures of exhibitions in the past:
Below is one of the prize-winning single-bloom chrysanthemums from this year's exhibition. The flower head would have been about the size of a slightly flattened, medium-sized cabbage.