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-Mangrove park-

“Characteristics of mangroves”

What is embryo seed?

The fruits of ordinary land plants leave the mother tree when mature, are sprayed by animals, wind, and gravity, and germinate after dormancy.
In the genus Hygiaceae, seeds germinate without resting in the fruit formed on the tree, and they grow by absorbing the necessary nutrients from the mother plant until it becomes a certain size seedling (about 1 year). And then leave the mother tree.
Such seeds are called embryo seeds, and seedlings that germinate on the tree are called propagules. After about 1 month, the fallen seeds open their leaves and the cotyledons become absorption organs.

Mangrove plants

-Characteristics of mangroves-

Mehirugi on the tidal flat.JPG


Mehirugi is one of the evergreen trees that form mangrove forests. It is also called "Ryukyu Kougai" because the fruit resembles "Kougai" (hairpin) in Ryukyu (Okinawa).

Seed ripening period

March to May

Average seed length

About 20cm

Leaf characteristics

Oval, thick and small. The surface is glossy.

Flower features

White petals that are relatively large.



In Japan, the distribution range of the Ohirugi is the second largest after the Mehirugi. Ohirugi has a strong similarity to tropical and subtropical plants because Amami Oshima is the northern limit of its distribution range.

Seed ripening period

October to May

Average seed length

About 16cm

Leaf characteristics

The tip of the leaf is pointed and is larger than Mehirugi.

Flower features

Red colored buds bloom.

What is an aerial root (respiratory root)?

-Characteristics of mangroves-

The aerial root is unique to Hirugi. Mangroves require a respiratory root because at high tide they are submerged under the water. There are several different types, plate roots, knee roots, octopus legs and others.

The Hirugi is characterized by the strange shape of the Aerial root (respiratory root). Once the respiratory roots of the Ohirugi emerge from the ground they bend and protrude in the shape of a knee on the surface of the water.


Ohirugi(knee root)

Shimashiraki(Octopus root)


Sakishimasuounoki(plate root)

Mangrove composition

-Characteristics of mangroves-

Major species

Ohirugi (Rhizophoraceae)

Mehirugi (Rhizophoraceae)

Secondary constituent species


akishimasuounoki (Sterculiaceae)
Shimashiraki [blind-your-eye mangrove] (Euphorbiaceae) Sagaribana (Lecythidaceae)

Okinawa Kyouchikutou [Sea Mango] (Apocynaceae) Shinokikazura (Fabaceae)
Nanten Kazura (Fabaceae)
Haemanju (Fabaceae)

Ibotakusagi (Verbenaceae) Hamagou (Verbenaceae) Hamabou (Malvaceae) Ouhamabou (Malvaceae) Kusatobella (Pittosporaceae)


Ryukyu Island pine (Pinaceae) Amamiakarasi (Fagaceae) Sharinbai (Rosaceae)
Itajii (Fagaceae)

Hamahisaki (Theaceae)

360° VIEW

-Characteristics of mangroves-


Mangrove sea side channel low tide 3.JPG
Mangrove waterway low tide (2).JPG
Mangrove sea side channel low tide.JPG
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