Rock Sweet Flag

There are two, possibly more, species of rhizomatous, aquatic perennials in this genus, which are found wild in N and E Asia, and N America. Variegated forms are popular ornamentals: the larger ones for waterside planting and dwarf varieties as pot plants or aquarium plants. Sweet flag (A calamus) has been cultivated and traded for over 4,000 years, probably reaching eastern Europe from Mongolia and Siberia during the 13th century, and spreading to western Europe in the 16th century. It was once important as a strewing herb and grown in large quantities in the Norfolk Broads in England, where it was gathered at an annual "gladdon harvest". Calamus candy, made by crystalizing tender slices of the rhizome, was popular in the 18th century as a medicinal lozenge to cure coughs and indigestion, and to ward off infection. There are several distinct populations of A. calamus in the wild, differing in genetic conformation and in important details of chemistry. Some botanists regard these as separate species. All contain 1-4 percent of volatile oil (oil of calamus) in the rhizome. The constituents of the oil may include asarone, a tranquilizing and antibiotic compound that is potentially toxic and carcinogenic. Oil from populations in N America and Siberia is asarone-free. Oil of calamus is banned by the US Food and Drug Administration. Doubts about its safety had led to withdrawal from general sale in other countries, including Great Britain, and use is restricted in Australia and New Zealand. Acorus gramineus was first mentioned as a medicinal herb in China during the Song dynasty (c.11-12th century).

Very variable, semi-evergreen perennial, with branched rhizomes and fans of glossy, linear leaves, 8-35cm (3-14in) long. Minute greenish flowers are borne in a spandix, 5-10cm (2-4in) long, in summer.


Common Name:
Rock Sweet Flag
Other Names:
Japanese rush, grass-leaved sweet flag.
Botanical Name:
Acorus gramineus
Genus:
Acorus
Family:
Acoraceae
Location:
E Asia
Cultivation:
Wet soil or shallow water up to 25cm (10in) deep in a sunny position. Acorus gramineus 'Pusillus' can be grown as a submerged aquatic. Plants grown in aquariums deteriorate if submerged for long periods, especially if grown in tropical conditions. Divide large clumps every 3-4 years to maintain vigor.
Propagation:
By division of rhizomes in early spring.
Harvest:
Plants are lifted at any time, except during the flowering period. The required amount of rhizome is cut and the remainder replanted. The rhizome may be dried for use in decoctions, distilled for oil (A. calamus), or used fresh for tinctures, liquid extracts, pastes, and powders.
Height:
10-50cm (4-20in)
:Width
10-23cm (4-9in)
Variations:
Hakuro-nishiki
Compact, with bright yellow leaves

Licorice (Licorice sweet flag)
Smells and tasts strongly of licorice
Height: 20-30cm (8-12in).

Ogon syn. Wogon
Cream-striped leaves
Height: 25cm (10in)
Width: 10-15cm (4-6in)

Pusillus (dwarf Japanese Rush)
The smallest variant with leaves 4-15cm (1½-6in)
long.
Height: 10cm (4in)
Width: 10-15cm (4-6in).

Variegatus
Leaves striped cream and yellow
Height: 25cm (10in)
Width: 15cm (6in)
Hardiness:
Z7-9
Parts Used:
Rhizomes (shi chang pu)
Properties:
An aromatic, anti-bacterial, tonic herb that stimulates the digestive system, clears the bronchial passages, relieves indigestion, and has mild sedative effects.
Medicinal Uses:
An important herb in Chinese medicine for poor appetite, gastritis, mucus, and depression. Considered to be a warming herb and therefore not given to patients with a tendency to perspire excessively.
Culinary Uses:
Known as sekisho in Japan, rhizomes are roasted or stir-fried. Licorice sweet flag is used to flavor rice in Thailand.
Bibliography:
Encylopedia of Herbs by Deni Brown Copyright ©: 1995, 2001 Dorling Kindersley Limited pp 101-102