Triglochin maritima in Miyajima Island

Triglochin maritima in Miyajima Island

Triglochin maritima L. (Japanese name: Shibana) is a perennial herb of the family Juncaginaceae, growing in brackish muddy areas.

An endangered species, Triglochin maritima, and brackish water environments

Seaside arrowgrass, Triglochin maritima L. (Japanese name: Shibana), is a perennial halophytic (saltwater loving) herb growing in coastal salt marshes. The leaves are linear with rounded tips, have sheathing bases, and are bright green in color. The flowers are small, green and arranged in erect racemes; the flowering season is September.

The Japanese name Shibana is a derivation of“shioba-na”: “shioba” means ‘salt field’ like a salt evaporation pond, and “-na” meaning a herb or vegetable.

The habitat of Shibana is brackish water environments which result from seawater and freshwater mixing together, with salinity conditions changing constantly, depending on tidal levels. The pond in the Tsutsumiga-ura Nature Park located on the northwest side of Miyajima Island is a brackish water habitat with surrounding brackish marshes where Shibana grows, along with Ruppia maritima L. (Ruppiaceae; Japanese name: Kawatsurumo) and Eleocharis parvula (Roem. & Schult.) Link ex Bluff, Nees & Schauer (Cyperaceae; Japanese name: Chaboi).

The plant Shibana is listed as an endangered species in the red list of Japan as well as the red list of Hiroshima Prefecture, although previously it was widely distributed from Hokkaido to Kyushu. This drastic decrease of Shibana has resulted from coastal development and reclamation, elimination of salt fields, and changes in nature. Currently, there are only a few places in Hiroshima Prefecture where the growth of Shibana is confirmed.

On Miyajima Island, sika deer have been observed feeding on Shibana. At this pond, the damage is controlled by protecting the plant with wire netting. Since 2002, local residents interested in the biological conservation of the island, volunteers of wildlife conservation groups, and students and researchers of Hiroshima University have been working to protect the plant and its habitat. A signboard has been placed near the pond to introduce the plant to visitors and call their attention to it and its significance.


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Seaside arrowgrass, Triglochin maritima L. (Japanese name: Shibana), is a perennial halophytic (saltwater loving) herb of the family Juncaginaceae growing in coastal salt marshes. The habitat of Shibana is brackish water environments which result from seawater and freshwater mixing together. The brackish water environment has its salinity conditions changing constantly, depending on tidal levels; this kind of habitat is a difficult place to preserve. The pond in the Tsutsumiga-ura Nature Park located on the northwest side of Miyajima Island is a brackish water habitat, whose surrounding area is brackish marshes where Shibana grows, along with Ruppia maritima L. (Ruppiaceae; Japanese name: Kawatsurumo) and Eleocharis parvula (Roem. & Schult.) Link ex Bluff, Nees & Schauer (Cyperaceae; Japanese name: Chaboi).

The Japanese name Shibana is a derivation of “shioba-na”: “shioba” means ‘salt field’ like a salt evaporation pond, and “-na” meaning a herb or vegetable. The leaves are linear with rounded tips, have sheathing bases, and are bright green in color. The flowers are small, green and arranged in erect racemes; the flowering season is September. This species is distinguishable from Ruppia maritima and Eleocharis parvula by its color and linear leaves.

The plant Shibana is listed as an endangered species in the red list of Japan as well as the red list of Hiroshima Prefecture, although previously it was widely distributed from Hokkaido to Kyushu. The reason for this drastic decrease of Shibana is the reduction in the environment in which halophytes grow due to coastal development and reclamation, elimination of salt fields, and changes in nature, etc., whereas in the past there were many suitable habitats along the Seto Inland Sea coast. Currently, there are only a few places in Hiroshima Prefecture where the growth of Shibana is confirmed.

On Miyajima Island, sika deer have been observed feeding on Shibana. At this pond, the damage is controlled by protecting the plant with wire netting. Since 2002, local residents who are interested in the biological conservation of the island, volunteers of wildlife conservation groups, and students and researchers of Hiroshima University have been working to protect the plant and its habitat.

The number of Shibana plants has increased from a few individuals to more than 100 in five years thanks to the conservation project. A signboard has been placed near the pond to introduce the plant to visitors and call their attention to it and its significance.

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