''Acorus gramineus'', commonly known as Japanese sweet flag, Japanese rush, grassy-leaved sweet flag, and grass-leaf sweet flag, is a botanical species belonging to the genus ''

Acorus ''Acorus'' is a genus of monocot flowering plants. This genus was once placed within the family Araceae (aroids), but more recent classifications place it in its own family Acoraceae and order Acorales, of which it is the sole genus of the oldes ...

'', native to

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...

, and eastern

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

. The plant usually grows in wetlands and shallow water. The genome of ''A. gramineus'' has been published by independent research groups in 2022 and 2023.

Description

This shrubby plant's long, narrow, slightly curved leaves may grow to 30 cm (12 inches) in height. It can grow fully or partially submerged, or in very moist soil, but it will usually only flower when at least partially submerged. Var. ''pusillus'' has slightly shorter, more rigid glossy green leaves, while var. ''variegatus'' has longer leaves streaked with yellow.

Cultivation and uses

''Acorus gramineus'' spreads aggressively by

rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...

, creating a nearly-seamless groundcover where conditions are favorable, and it is frequently used around the edges of ponds and water gardens, as well as submerged in freshwater aquaria. It can be propagated by dividing the fleshy underwater rhizome and planting the base in shallow water. In Japan during the

Heian period The is the last division of classical Japanese history, running from 794 to 1185. It followed the Nara period, beginning when the 50th emperor, Emperor Kammu, moved the capital of Japan to Heian-kyō (modern Kyoto). means in Japanese. It is a ...

, leaves of the plant were gathered for the Sweet Flag Festival on the fifth day of the fifth month. Sweet flag and wormwood were spread on the roofs of houses for decoration and to ward off evil spirits. Special herbal balls made of sweet flag were also fashioned for the occasion.

Notes

References

* * {{Taxonbar, from=Q2544575 Acorales Freshwater plants Medicinal plants of Asia Plants used in traditional Chinese medicine Ornamental grass