This is the
Japanese form of
Chinese zi3-su1 - "purple
su".
Vietnamese tia to renders the same Chinese word.
Su seems to be the ancient name of this plant, and the same word is also often used in the sense "to be revived" (from death or inebriation), which suggests early associations of its strong smell. Another ancient name is gui4-ren4, "tender-leaf of the cassia", evidently also suggesting its fragrance and the feeling of the leaf. As su it appears in Chinese literature from the Han dynasty onward. The usual English name is "beefsteak leaf", and the plant is classified by botanists as Perilla frutescans. For medicinal use the leaf is usually harvested in September. Many parts of the plant are used medicinally, but only the leaf has wide culinary application.
There are red (actually, purple) and green varieties. The leaf is soft and broad, somewhat wrinkled-looking, and has many points.
Its taste is unforgettable but difficult to describe - it reminds me of certain members of the mint family, but it is far more seductive and complex. It is best known in the world at large in Japanese cuisine. Its two commonest uses there are with sashimi, where it complements the slipperiness and mildly fetid smell of the fresh raw fish, and in the preparation of umeboshi, for which it is pickled along with the plums, giving the final product a reddish-purple color. I find that most of shiso's elegant flavor is lost in the strong-tasting umeboshi preparation.
Red shiso is also eaten in Japan pickled, and sometimes then dried, as a condiment.
I am grateful to
gn0sis for pointing out that many pickles other than umeboshi (such as
shichifukujinzuke and the
preserved ginger called
beni shouga), and also certain forms of the distilled liquor
shochu, are colored and flavored with shiso.