Floridata Plant Encyclopedia

A Floridata Plant Profile 852 Acorus gramineus

Common Names: Japanese sweet flag, Japanese rush, grassy-leaved sweet flag, dwarf sweet flag Family: Araceae (arum Family)

Japanese rush
This is the popular golden variegated Japanese sweet flag cultivar 'Ogon'.


Japanese sweet flag is an aquatic or wetland perennial with semievergreen grasslike foliage. It has narrow, 6-14 in (15-35.6 cm) glossy leaves and looks like thick, lush grass. The leaves are carried in two ranks, like opposing fans. They are flat, about a 0.5 in (1.3 cm) wide and tend to flop over. The insignificant flowers, shaped like little horns, are produced in midsummer on erect hollow stems. Usually only plants grown in water produce flowers. The cultivar, 'Ogon' (a.k.a. 'Wogon') is also called golden variegated Japanese sweet flag, or Japanese rush. It has arching foliage with cream and chartreuse stripes, and is a little smaller than the species, with leaves a 0.25 in (0.6 cm) wide and just 10 in (25.4 cm) long. 'Variegatus' has green and white striped leaves. 'Licorice' has foliage and rhizomes that smell like anise. 'Minimus', and 'Minimus Aureus' which has yellowish leaves, are tiny cultivars, only 3 in (7.6 cm) tall and suitable for aquaria and small pots.


Acorus gramineus, the Japanese sweet flag, is native to eastern Asia where it grows in wetlands and shallow water.


Light: Full sun to partial shade. Moisture: Japanese sweet flag requires very moist soil. It does just fine in the wetland zone along ponds and ornamental pools, and even submersed in water 3-6 in (7.6-15 cm) deep. It can be grown in regular garden situations but must be watered frequently. The leaf tips will turn brown and wither if the soil dries for even brief periods. Hardiness: USDA Zones 6 - 9. Propagation: Propagate Japanese sweet flag by dividing the rhizomes in spring, then letting the new divisions get established in a pot for a few weeks before planting out.


Japanese sweet flag is used along pond margins and at the edges of water gardens. It's a great foliage plant for shallow water and marshy areas. It spreads aggressively by rhizomes and will eventually produce a seamless turf, making a beautiful groundcover for the front of a bog garden. When walked upon, it releases a fragrance reminiscent of cinnamon. If you don't want a solid stand of Japanese sweet flag, grow it in submerged containers so it can't spread. In Japan, the smaller cultivars often are grown in shallow water in containers indoors.


There are only two species in the genus Acorus. The other is A. calamus, or sweet flag, the source of oil of calamus, used medicinally and in perfumes and soaps. Sweet flag was formerly used as a "strewing herb', to spread on the floor so that a pleasant scent would be released when trod upon. Japanese sweet flag is not quite as aromatic as the true sweet flag. Although the sweet flags are in the Jack-in-the-pulpit family, their flowers don't look much like the typical spathe and spadix of most members of the family.

Steve Christman 11/8/00; updated 10/22/03

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Acorus species profiled on Floridata:

Acorus gramineus

( Japanese sweet flag, Japanese rush, grassy-leaved sweet flag, dwarf sweet flag )

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