Cobra lily Urashima

Cobra lily Urashima is a perennial belonging to the genus Arisaema, which has pseudo dioecism.   It grows up to 30 to 60cm, sometimes reaching about 80cm in height.   It is endemic to Japan and grows naturally mainly in Honshu and the Shikoku region and also in the Hokkaido region and some parts of the Kyushu region.   Cobra lily Urashima likes rich water and weak light and its preferable habitat is areas under forest that get little direct sunlight.   Consequently, it often grows on forest floors near to a seashore or human habitation.

Cobra lily Urashima forms the oblate spherical corm in the underground.   It sprouts to develop one leaf from about March to May.   The petioles (leaf stalks) of the leaf wrap around the whole circumference of the peduncle (flower stalk) to be cylindrical and to form the pseudo-stem.   Whereas, its upper part develops 11 to 17 leaflets.   The leaf begins to die from summer and is defoliated usually by the end of summer.

The peduncle stands upright from the pseudo-stem to form spadix having one spathe, which characterises the family Araceae.   The spadix normally develops either male florets or female florets.  These florets are usually hidden by the spathe.

The appendix of the spadix develops gradually thinner like a string to extend long out of the spathe.   Sometimes it reaches about 70cm in length.   Owing to this appearance, the leaflets are said to resemble a straw skirt; traditionally worn by hunters and fishermen in Japan.   The string is compared to Taro Urashima who drops his fishing line from his fishing rod, and accordingly, it is named Urashima-so in Japanese.   Its variation name also came from this, Urashima.

Cobra lily Urashima is dioecism.  The gender is changed by the plant's size, which characterises the family Arisaema.   When its plant body is small, Cobra lily Urashima is in the vegetative phase and differentiates and forms only vegetative organs, such as leaves or stems.   At that time, it is asexual.  After that, when the plant body grows larger to some extent, it enters the mature phase to develop male florets.   When it grows even more, it develops female florets.

Cobra lily Urashima is pollinated by the relatives of Mycetophilidae.   It produces corn-like multiple fruits that closely resemble the fruits of Jack in the pulpit (Arisaema serratum (Thunb.) Schott) in Autumn.   It is green in colour at the beginning but matures into a vibrant red.  Each fruit contains 0 to several seeds.   The fructified peduncle remains until late autumn having red ripen fruits.  The peduncle falls down in winter to be dormant in the state of just corm.   This corm often produces cormlets around itself.

Cobra lily Urashima contains saponin and calcium oxalate, mainly in the fruit and the corm, therefore it is poisonous.

Classification: Araceae Arisaema
Scientific name: Arisaema thunbergii subsp. urashima (H.Hara) H.Ohashi & J.Murata
Japanese name: Urashima-so
English Name: Cobra lily Urashima
Native locality: Japan (Honshu, Shikoku Region and some parts of Hokkaido and Kyushu Region)
Ecological description: Perennial
RDB : ---
Planting place: Japanese Garden
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