Japanese rush, Grassy-leaved sweet flag, Grass-leaf sweet flag, Acorus gramineus var. pusillus, Acorus gramineus var. variegatus
Family
Acoraceae (sweet flag family)
Origin
Japan, Korea and eastern Asia
Water
freshwater
Maximum size
30 cm
Temperature
10–24°C
pH
6–8
Hardness
Tolerant (estimate)
Care level
intermediate
Lighting
Medium to high light; CO2 not needed
Care
Japanese sweet flag is a small, grassy relative of sweet flag (family Acoraceae) from Japan, Korea and eastern Asia. It grows in wetlands and shallow water and spreads by rhizome into dense clumps. It can grow fully or partly submerged, or in very wet soil, but it usually flowers only when partly out of water. It has long been sold for aquariums, but it is really a bog or marginal plant. Underwater it grows slowly and tends to decline over months, so it is best used at the edge of a pond, in a paludarium, or with its leaves above the water. Leaves reach about 30 cm. The dwarf variety pusillus has shorter, stiffer, glossy leaves; variegatus has longer leaves striped with yellow. It tolerates cool water and suits coldwater tanks and ponds better than warm tropical aquariums. Water figures are our estimate, not from the sources. Sources: Wikipedia (en.wikipedia.org/wiki/Acorusgramineus); Wikipedia, List of freshwater aquarium plant species. Checked October 2026.
Breeding
Divide the rhizome and plant the pieces with the base in shallow water or wet substrate.
Compatibility and tank mates
Tough leaves are generally ignored by fish. Suits coldwater tanks, paludariums and pond edges; tends to fade if kept fully submerged in warm tropical tanks.
Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.
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