"What's this flower?"
"That plant is a member of the same family as taro."
"Can you eat it? Those berries looks pretty big."
"Well. . . something, probably deer, do sometimes munch on the flowers, but if you eat it, oxalic acid molecules the shape of little needles will probably tear up your throat so badly it hurts to breathe."
"Oh. . . What's it called?"
"In English, we just call it the Japanese arisaema, but look at the coloration of the stalk. Does that remind you of snake skin? The Japanese call it mamushi-gusa, the pit-viper weed. Still want to try eating it?"
While A. serratum (synonymous with A. japonicum, but that's another can of worms!) can be found throughout Japan and is one of the most conspicuous flowers around here, there are some 30 species of arisaemas in Japan, from Okinawa to Hokkaido, and over 150 species of arisaema worldwide, but you do have to get away from the cities to find them. People in the Northern hemisphere may be family with jack-in-the-pulpit.
The Toxin: Raphide
Elephant's ear looks
similar to taro.
|The garden variety of Monstera is both beautiful |
and tasty if eaten properly.
Of course, the reason these plants stand out so much are the shape of the pitfall-trap flowers. Carnivorous plants are famous for pitfall traps, but arisaemas simply use them as a pollination strategy. In the case of arisaemas, these organs are composed of a central stalk, called a spadix, the lower half of which is covered in tiny flowers, and a surrounding vase-like leaf, called a spathe. Insects crawl down the spathe to the flowers and have a hard time getting back out. Male plants have an opening at the bottom of the spathe, so that insects will cover themselves with pollen as they crawl down the length of the flower to escape. Female plants are not so generous.
|Left: Male flowers on the spadix. Right: Opening for insects to escape|
|Left: Female flowers. Center: No opening for insects. Right: Insects trapped inside.|
|A. thunbergii subsp. urashima|
with a beautiful array of
leaves and an extended spadix.
|Fruiting A. serratum|
Find Them before They Find You!
|An unusual specimen of A. serratum with|
two stalks. A week later one flower has
been lopped off and has bite marks. Were
the deer confused by the twin stalks?
Information about sex-changing of arisaemas is discussed in depth in
Kinoshita, E. 1987. Sex Change and Population Dynamics in Arisaema (
and a review is given by
Srivastava, P. and Banerji, B.K. 2012. Gender biasing in Arisaema – a unique and rare phenomenon. Current Science, 102:189-193.
A casual overview of A. serratum in Japanese with a photo of dead insects inside a fruiting flower can be seen at
Examples of toxic plants containing raphides from
初島住彦監修, 屋久島の植物(新版). 2001：南方新社
片野田逸朗, 九州野山の花. 2004：南方新社
It makes my head spin, but if you really want to debate names, i.e. A. serratum versus A. japonicum, then you can look up
邑田 仁、大橋 広好. 2009. 牧野富太郎とマムシグサの分類(日本植物分類学会第7回東京大会公開シンポジウム講演記録 「牧野富太郎博士の植物研究とその継承」) [Taxonomic history of Arisaema serratum and A. japonicum] 分類9(1):37-45.
Toxicity information and counts of poisoning incidents (I understand why little kids might eat them, but apparently some adults mistake the blood-red berries for corn? ?) are listed in
Ministry of Health, Labour and Welfare: 自然毒のリスクプロファイル：高等植物：テンナンショウ類 (visited on April 17, 2014).