In Japan in the fall, elaborate displays of chrysanthemums, or kiku, are everywhere, from parks to shop windows. This year, however, New Yorkers need go only as far as the Bronx to get a glimpse of this centuries-old tradition. As the result of a five-year collaboration between the New York Botanical Garden and the Shinjuku Gyoen National Garden in Tokyo, on October 20 the Botanical Garden will unveil the most extensive display of chrysanthemums cultivated in the imperial style that has ever been seen outside of Japan.

The exhibition was the idea of the Botanical Garden’s former director, Kim Tripp, but what really made it possible was the hard work and close collaboration of two people: Yasuhira Iwashita, the kiku master at Shinjuku Gyoen, and Yukie Kurashina, a gardener at the Botanical Garden, who spent many months in Japan over the last few years training with Mr. Iwashita and absorbing the traditionally secret art of kiku cultivation.

At Shinjuku Gyoen, Mr. Iwashita and his staff train chrysanthemums in seven styles, for an annual exhibition in the first two weeks of November. Until World War II,

Shinjuku Gyoen was the private garden of the imperial family, and the traditional styles of kiku cultivation were originally designed to celebrate the November 3 birthday of Emperor Meiji, who ruled from 1868 to 1912.

With Mr. Iwashita’s consultation, Ms. Kurashina chose just three of the seven styles to grow here: ogiku, or “single-stem,” kengai, or “cascades,” and ozukuri, or “thousand bloom.” In 2004, Ms. Kurashina spent six months in Japan, training intensely with Mr. Iwashita. In 2005, she experimented with growing the plants at the Botanical Garden for the first time, while also making several trips to Japan.

This is now the third year Ms. Kurashina and her colleagues have grown and trained the flowers, and they have mastered every detail, from the makeup of the soil to how much humidity the plants want, to how to get them to bloom just at the right time. The exhibition at the Botanical Garden is opening earlier than — and running twice as long as — Shinjuku Gyoen’s exhibition. For that reason, half the plants have been shaded for a certain period each day, to fool them into thinking that it is later in the fall and make them bloom early. After two weeks, they will be switched out for other, later-blooming plants. (All of the kiku styles will be displayed under traditional bamboo pavilions, called uwaya, in the Enid A. Haupt Conservatory courtyard.)

All three styles — ogiku, kengai, and ozukuri — originate from tiny cuttings. Some of the varieties being used for the exhibition had been saved at the Botanical Garden since the last chrysanthemum show, over 20 years ago; others were ordered from a nursery in California.

The ogiku, or single-stem plants, are planted in the spring. By showtime, each plant will consist of a very tall stem with no side shoots and a single blossom at the top. As is traditional, they will be arranged in tight rows of pink, yellow, and white flowers — a pattern designed to mimic the stripes on the imperial horse bridle.

For the kengai, which in their finalformarecascadesofsmallblossoms resembling flowers growing down a cliff, the shoots are planted earlier, in mid- to late December of the previous year. They grow straight up for several inches, and then the gardener bends them on a diagonal. Sideshootsare”pinched” — that is, the growing shoot is pinched off, which makes it grow side shoots, so that eventually there is a thick forest of small stems, each with its own buds. The stems are eventually tied to a frame, which, ultimately angled downward, produces the cascade effect.

The ozukuri grow for the longest amount of time — the shoots are planted in mid-November — and require the most skill to grow successfully, Ms. Kurashina said. The literal meaning of ozukuri is “to make big,” because the final plants must be 8 or 9 feet across. Ms. Kurashina facetiously compared these plants’ cultivation to the production of foie gras, since she and the other gardeners have in a sense force-fed the plants with all the right conditions for prodigious growth. In particular, during the winter, the gardners turned the lights on in the greenhouse for several hours each night, so that the plants would think the long night was actually two short nights, divided by a day, and would concentrate their energy on growth instead of blooming .

The gardeners started with 100 cuttings, which over the months have been winnowed down to 12 plants, of which only six will be exhibited in the courtyard. First, they selected plants that grew five branches, since that pentagonal shape is the best to produce the dome-like form of the ozukuri. They pinched the shoots to produce more side shoots. By last week, the plants had been attached to their aluminum frames, and the branches were starting to produce buds. In the end, each branch will have one flower, and each plant will have between 200 and 300 blossoms.

In an interview, the vice president for horticulture and living collections at the Botanical Garden, Todd Forrest, said that the kiku exhibition is the most elaborate plant show the institution has ever done, as well as “the most incredible cultural exchange that [it] has been part of.” The exhibition has been sponsored by several Japanese corporations, including Mitsubishi, Canon, and Toyota, and it will be accompanied by an array of programs celebrating Japanese cultural life, from an exhibition of works on paper featuring Japanese plants in the LuEsther T. Mertz Library gallery, to workshops on origami, bonsai, and ikebana, the Japanese art of flower arranging, as well as musical and dance performances.

Ms. Kurashina expressed enormous gratitude to Mr. Iwashita for his patient teaching. She imagined that, like a traditional Japanese “master,” he would be imperious and severe. Instead, he was enormously courteous, even deferential, to his staff and apprentices. Because Ms. Kurashina has lived in America for almost 20 years, she was willing to be more demanding than the typical apprentice. “I’m very glad I was half-Americanized, because I was aggressive enough to ask [questions],” she said.

She told the story of one longtime gardener at Shinjuku Gyoen whom all the apprentices shied away from, because he seemed unfriendly; whenever an apprentice would approach to see what he was doing, he would immediately walk away. “I sensed he was just shy,” Ms. Kurashina said, “so I said, ‘Don’t go anywhere! Stay and show me what you’re doing!'” And, in fact, the gardener was happy to teach her.

Part of the reason Mr. Iwashita was willing to share his knowledge with her and her colleagues, Ms. Kurashina said, is that the art of kiku cultivation is on the verge of disappearing in Japan. The best gardeners, like Mr. Iwashita, are near retirement, and young people are uninterested in learning the traditional techniques. Ms. Kurashina herself had some exposure to training chrysanthemums in the gardening club at her university in Kyoto, but she “didn’t pay too much attention” and never expected to work with chrysanthemums again, she said. In the early 1990s, she came to study at the New York Botanical Garden School of Professional Horticulture in order to learn the techniques of traditional American and English gardening.

Now, though, she has a new and deep appreciation for the art of kiku, which she hopes that others — both Americans who visit the exhibition, and Japanese who hear about it — will come to share. “I’m hoping that this exhibition has some impact on Japanese people— that they recognize that we have this beautiful tradition” and keep it from dying out, she said.