It's really about the shift to autumn. Until the autumn equinox, you can still feel the lingering summer heat, and on the 9 IX, of course, you have 菊の茶. Then, suddenly, the temperature drops and you can see the autumn grasses. Around this time, moon viewing parties and with it, wild geese as a motif, become common.
Microseasons
生年と歿年の間露けしや(せいねんと ぼつねんの間 つゆけしや, the interval / between birth and death / heavy with dew; by Tanaka Hiroaki, 1959-2004). Here 露けし is a seasonal word, as in this season we start to see dew in the mornings as it gets colder during the night.
22 IX to 27 IX: 雷乃収声(かみなり すなわち 声を おさむ, thunder lowers its voice). After the autumn equinox, the summer heat dies and summer's thunder gods go to sleep.
菊
9 is the zenith of yang; so this should be the most auspicious of the Schnapsfeste.
Chryanthemum liquor is quite common: A few petals in sake; or maybe as a お白湯?
Yellow and white colour combination alone might be good to evoke chrysanthemums.
懐石
Flounder (🇩🇪 Flunder, Butt) in autumn it is quite fatty and good for
刺身, or stewed
-
Quince: often candied; or just in a basket to give off a nice aroma. Might be a good idea for a 床 decoration instead of a
香合
花
From Mittwer's book, which is Eulalia, burnet-bloodwort, smartweed, pigeonberry, pink in a Bisk-ware octopus-trapping pot
From Sen's Chadō, which is 木槿.
According to the Chadō Textbook:
はぎ (Buschklee)
すすき (Chinaschilf)
葛(くず)
なでしこ / せきちく (Chinesische Nelke)
おみなえし (Goldbaldrian)
ふじばかま (Wasserdost, Wasserhanf)
ききょう (Ballonblume, Chinesische Glockenblume)
しゅうかいどう (Begonie, Schiefblatt)
ほととぎす (Japanische Krötenlilie)
みざまりんどう (Enzian)
しゅうめいぎく (Herbst-Anemone)
和菓子
From Sen's Chadō, which is こはぎ 餅 (bush clover, one of the seven autumn grasses)
For 干菓子, it's raw sugar shaped like taro, and like the leaf of it.