Arisaema serratum: Toxic, sex-changing perennials with pitfall-trap flowers and blood-red berries.

Arisaema serratum, the Japanese arisaema, is one of the most conspicuous flowers along the trail from late March through September.  It may be the perfect flower for the Gothic gardener. Visitors inevitably point to the flowering stalks or the clump of bright red berries and ask,

"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

Alocasia odora,
Elephant's ear looks
similar to taro.

This genus is in the Araceae family. The Japanese know this family best for taro, or satoimo in Japanese. This is a delicious tuber, but it is not eaten raw because of the presence of calcium oxalate crystals. If you've ever had a kidney stone, then you can probably blame the  formation of calcium oxalate within your body. (Note: I don't believe this is related to ingestion of calcium oxalate.)  Needle-shaped molecules of calcium oxalate, called raphide, are produced by many plants to deter foragers. Side effects of ingestioArisaema thunbergii Blume subsp.n can range from tingling in the tongue and mouth, to inflammation of the throat so severe  that the victim has trouble breathing. In the past 50 years, there have been no records of anyone dying from eating A. serratum in Japan, but there have been several hospitalizations. There is another member of this family, Alocasia odora, called Elephant's Ear in English, that visitors often confuse with taro, with similarly unpleasant consequences and a trip to the hospital. The Japanese name for Elephant's Ear is kuwazu-imo, meaning inedible potato. Other plants containing raphide include philodendrons and schefflera, that, together with Elephant's Ear, are often used as ornamental plants in the West. If you want to try the tingling, without hospital bill, then look for the fruit of the monstera plant, also a member of this family. (Oh, but Do Not attempt to eat the rind like the fool I was!)

The garden variety of Monstera is both beautiful
 and tasty if eaten properly.

Pitfall-trap Flowers

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.

Male flowers:

Left: Male flowers on the spadix. Right: Opening for insects to escape

Female flowers:

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.

One of the beautiful species of arisaema in Yakushima is called A. thunbergii subsp. urashima. The spadix has a long extension used to lure insects inside. This whip-like extension has been likened to a fishing rod, perhaps the fishing rod of Urashima in the legend of Urashima and the sea turtle kingdom. (I imagine this works the same way fly tape does:  Just try hanging a piece of string from the ceiling and open the window. Flies apparently like to land on long, skinny things.) Because of the shape of the flowering organs, Arisaemas are sometimes referred to as cobra lilies. However, true cobra-lilies are an unrelated species that captures insects for the purpose of eating, while, in the case of Arisaemas, insects become casualties of pollination and their dead bodies simply accumulate inside female flowers.

Sex-Changing Habits

Fruiting A. serratum

Okay, so I still haven't touched on what many botanists consider the most interesting trait of arisaemas: Labile sex-changing, the ability to change sexes based on growing conditions. Arisaemas are perennials that die back every year, although the underground tumor, called a corm, can continue to produce flowers for 20 years or more.  Apparently, a small corm tends to produce strictly male flowers, but when the corm grows large enough, they produce only female flowers. The reverse, although rare, is also possible. So imagine a large female specimen producing a bunch of berries that will likely fall to the ground uneaten and later spring up as males around the mother plant.


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?

A. serratum is especially common along roadsides and mountain trails up to elevations around 900 m. The stalks start popping up in February and even after the flowes wilt, the bright, blood-red berries will remain, uneaten until after summer ends. (A. serratum is so abundant, that it got all the attention when I was training, and I ignorantly assumed it was the only Arisaema on the island! Well let me make up for that oversight now!) Look for A. urashima in the spring, from coastal plains and along the trails up to around 800 m. A. sazensou and the rare A. longipedunculatum can also sometimes be found along trails in late spring to early summer. Elephant's ear grows abundantly at low altitudes, and monstera is often found in gardens.

A. longipedunculatum

~~~~~~~~~~~~~~~~~

Information about sex-changing of arisaemas is discussed in depth in
  Kinoshita, E. 1987. Sex Change and Population Dynamics in Arisaema (Araceae). I. Arisaema serratum (Thunb.) Schott. Plant Species Biology 2:15-28.

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

A. sazensou

  http://www.fukuoka-edu.ac.jp/~fukuhara/keitai/mamushigusa.html .

Examples of toxic plants containing raphides from
  http://www.aspca.org
  http://www.petpoisonhelpline.com .

Species identification:
  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  
  登田美桜、畝山智香子、春日文子（2013）過去50年間のわが国の高等植物による食中毒事例の傾向、食衛誌55(1):55-63.
   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).

*edited on 1/15/2015 to correct the synonym Arisaema urashima to A. thumbergii subsp. urashima.

A. serratum

Tankan Oranges

From that oranger-than-orange color to the rich, delectable flavor, tankans are my favorite citrus, no questions.

I can remember my dad sitting in our backyard when I was growng up, eating oranges until supper time, a pile of rhinds slowly growing beside him. I've turned into my dad.

This year, the farmers have just celebrated the end of their harvests, and the tourists are scrambling for the last few available boxes of premium fruits. Fruits lacking in appearance will go into jams and juices. It seems like a good time to consider the question: What exactly is a tankan?

The last of the Tarumi #1's
waiting for  selection
and shipment.

By the Wikipedia definition they originated from a spontaneous hybrid of a tangerine and a naval orange. Tankans were first introduced to Japan from Taiwan, and production in Yakushima started in earnest 55 years or so ago. Today, they are one of Yakushima's main exports, and the harvest season is from February to early March. So just when Japan could use an extra dose of vitamin C to fight off the flue season, the tankans come into season, said to be packed with twice the vitamin C of mandarin oranges.

Okay, who do these belong to?
Somebody left this odd pair
at the bus stop.

The little fruit covers would be
cute even if they weren't pink!

Don't forget ponkan tangerines!

"Correctly" peeled tankan rhind.

You can find two strains of tankans in Yakushima, although few people could identify them at a glance. There is the zairai, or heirloom, variety, and the selectively bred Tarumi #1. The zairais hit the market well before the warmth of spring has come. They have an intense flavor that I love, but many people are turned off by the abundant seeds. The Tarumi #1 is sweeter, usually bigger, easier to eat, and has very few seeds.

But even within each strain, there is a lot of variation depending on growing conditions. I asked a grower at the end-of-harvest dinner about this and learned the following: Fruits growing near the bottom of the tree tend to have more nutrients, and therefore have more concentrated qualities, while those too near the top may be watery, or have a big, bubbly appearance. Later, while trying my hand at fruit QC, I learned that the vibrant orange color depends on exposure to direct sunlight, and those growing in the partial shade of a leaf or two develop a nice gold-to-orange two tone skin. Flavor and nutrition content also depend on exposure to sunlight.

So if sunlight is good, what's the deal with all those socks? Hehe. Those covers are meant to keep the  brown-eared bulbuls from pecking holes in all the fruits. I don't know if it works or not, and not everybody uses them, but they sure look cute!


I should also mention Yakushima's other big citrus export, ponkan tangerines, which have been grown in Yakushima for 90 years. If the Tarumi #1's aren't mellow enough for you, then ponkans, harvested in December through January may fit the bill.


And finally, how to eat a tankan: It's hard to go wrong, but the general opinion is that it's easiest to peel it from the bottom and work around in a circle like you would peel an apple.

Sanbon Sugi gets a physical.

If you've been following my blog, you may know that visitors can no longer see Jomon Sugi from the "front," because a health exam a little over a year ago found that the overhanging limb is hollow -- as it may have been for hundreds of years -- and was deemed hazardous to those standing below. But just how do you go about evaluating the health of a tree that's older than Jesus?

This January, I went to the local Forestry office and asked. Fully expecting to be shown a stack of papers and research reports, I was thrilled by the answer:

Why don't you come along and see for yourself?

平成24年11月、縄文杉の正面の枝が空洞だ（←たぶん大昔から）とわかって、下の展望デッキに立っている登山者の安全を確保するため、林野局の判断に従って、展望デッキの半分が立入禁止となった、とごご存じでしょうか。でも、縄文時代から生きてきたものの場合、健康診断はどうやって行われているでしょうか。林野局の保全センターに聞いてみたら、その答えは、

 調査結果を読んでもいいけど、その代わりに、今度、見学に行ったら？

The Patient: Sanbon Sugi

The next examination coming up was for a tree named 三本杉 -- Sanbon Sugi, or, literally, Three Sugi Trees, in English. This tree isn't on the list of milleniarians, but, according to the head of the research team, it received its name well before any of its famous Yakusugi associates. Not only does this threesome of inosculated (I'm impressed if you don't have to google inosculation!) trees stand along the

That's a bottle of
Mitake shochu behind
the inscribed stone.

Kusukawa Trail used by Edo-period loggers to access Yakushima's interior, but it's a holy tree. In fact, there is a small shrine recognizable by the carved stone nestled among the trunks. Over hundreds of years, the tree has grown up around this stone, so that the dedication is only partly visible.

次の調査の対象は三本杉でした。まだ屋久杉と呼ぶほど古くない杉ですが、現在屋久島の他の著名杉の名前が決まった断然前に、この不思議な杉は三本杉と名づけられました。三本の大きな杉が合体してるかたちで、江戸時代にも伐採のために使われた楠川歩道に立っています。数百年渡って、幹と幹の間においてある碑の字を二つしか見えないほど木が成長しています。

Sanbon Sugi, measurement sticks
in place.

Once there, the head scientist bowed to the shrine, and then they set up tools for standard measurements, laying out tape measures and standing a ten-meter-high pole next to one of the trunks. We all backed away and tried to estimate the height of the tree -- not an easy feat in a dense forest. I counted out 24 meters to a space where I could see both the top and bottom of the tree, and then took out my cell phone (got to love smartphone apps!) to measure the angle. Others estimated how many ten-meter poles would be required to reach the top. The team leader, a local well-versed in both about nature and local lore, took out a surveying device that looked a bit like a mini-telescope that measured both and angles to calculate height. Most estimates fell around 24 meters, although both my cellphone and the surveying device gave something closer to 30m. The leader jotted down the height and environmental conditions and sketched the tree on the long form he carried.

班長がお参りをしてから、研究者達はメジャーなどを広げたり立てたり、様子を確認しました。そうして、皆さん、三本杉から下がって樹高を推測しようとしました。木々が密生している森の中には、大した技です。10メートルの棒を水準にして推測したり私は携帯のアプリを使って、角度と距離で推算しました。班長はそれを自動的に図って計算する装置を出してが、意外に高い数字（約30m）が出ました。（目で推測すろと、24mぐらいではないかと思っていました。）

Circumference is measured at the highest point 1.3 m above the ground. Coins removed and returned to the shrine. Did you know one-yen contain aluminum, which is bad for the environment? Soil Observations: Testing the firmness of the soil. Note the book of swatches on the ground.

The next measurement was circumference (and thereby diameter) of each trunk. This is measured at 1.3 meters from the ground, so that the sprawling roots don't overblow the measurements. Then parameter of the roots. What trees (epiphytes) had taken up root on Sanbon Sugi. (It's not easy to identify a plant that's 12 meters up the side of another tree trunk!) and what plant species were growing in the area. The depth of hollow openings above the roots. A sound-test for hollowness. (All three trunks are hollow.) Estimating how far the branches extend in all directions. The presence of fungus on decaying limbs. (The form called for identification of the fungus, which is something I couldn't do with the fungus in front of my nose, and this fungus was probably 15 meters above.　サルノコシカケ, polyporaceae, seemed like a good bet.) Things like that. 次は各幹の胸高周囲（地面から1.3mの高さで周囲を図る）、根っこの周囲、着生植物の種類（難しい！）、付近に生えている植物、空洞状態のテスト（各幹、皆空洞です。）、枝の延長、菌類の有無と週類。（感動しますは。菌類のわからない私は、十数メートル頭上の菌類の種類の判断は無理です。サルノコシカケかな。）などなど。 Lunchtime was the most interesting for me. I'd racked up a bunch of questions I wanted to ask, but found it was much more interesting to let the group talk about things I hadn't even considered. 昼ご飯の会話もかなり面白かったです。いろんな聞きたい質問がありましたが、皆さんの話しが面白すぎて、ほとんど聞き忘れました。特に班長は自然についても里についても詳しいです。 In the afternoon we started the soil measurements, which take the most time. A couple holes were dug and the leader expertly documented the soil layers including color, granularity, stiffness, and a bunch of other factors I didn't understand. Apparently these things have been recorded for soils all over Japan, and you can look up the color in this little booklet that must be the world's most expensive book of swatches (to untrained eyes, just like you get for free from the paint store!) to find out the stage of erosion. While the leader concentrated on that the rest of the team took turns boring meter-deep holes by dropping a weight on the end of a sharp-tipped pipe. With each drop, the pole sank a few milleters or maybe even a couple centimeters, and the depth was recorded. The weather forecast had called for partly cloudy skies, but it was much chillier than most of us had anticipated, and I found myself cheering for the pole to sink faster as a shivered and waited.

午後になったら地質を調べました。結構時間がかかりました。穴を掘って、土壌の色、硬さ、粒子の大きさ、などなど。日本の各地でこれらがすでに研究されているため、（めちゃくちゃ高い）本で色を検索したら、土壌の腐食度合いを調べられるらしいです。班長が詳しい観察を行いながら、残りは重りの付けられている棒で4つの穴を作って、土壌貫入式を行いました。重さを上げて、落とす度に棒が少しずつ地面に入り込んで行きます。その深さを記録しながら１mの深さまで繰り返す作業です。天気予報は晴時々雲でしたが、とっても寒かったです。その土壌貫入式棒を見つめながら手が震え始めそうになりました。

While the team was documenting all the flora in the area, (omg, they're supposed to know the names of all those ferns?? Wow.) a family of monkeys -- apparently aquaintances of our leader -- stopped by to chat as they foraged nearby.

研究者達が植物の種類の記録していた時、（皆さんはとても詳しいです。特にシダの区別が難しそうです！）数匹のサルたちがよってきました。班長の知りたいみたいに、遊び声をかけたり、うちたちが研究作業に励みながら、サルたちは採食行動に励んで、面白かったです。




Sanbon Sugi (according to Yakusugi Museum texts)
Height: 23.4m
Circumference (of largest trunk): 4.9m
Elevation: 550m

Special thanks to the kind and knowledgeable folks in the forestry office and at the Yakushima Forestry Conservation Center.

林野局や屋久島森林生態系保全センタの方々にとても感謝しています。

Ja no Guchi Waterfall

Just a bit further. . .

It was September of 2009 when I first got on the Jetfoil to Yakushima with a bunch of curry packets, a tent, and a jacket stuffed into my bag and not a clue as to what I was doing. On the way to my seat, I picked up the largest brochure with a map of Yakushima, and the first thing to catch my eye was the Ja no Guchi waterfall.

Blanaphors:
Parasitic plants commonly
seen in autumn.

The hike to Ja no Guchi shares none of the fame of Shiratani's moss forests or Mt. Miyanoura's sub-alpine grandeur, but it has some good points. For one, there's no big steep elevation change, so if you've already hiked a big one, and you're looking for a low-key day for recovery, this route may fit the bill. Oh, you'll still want your hiking boots: You might even miss Jomon Sugi's staircases and boardwalks when you have to scramble over boulders at the brook adjacent to the waterfall, and there's a detour along the way that takes you over a small hill where you'll probably use your hands to pull yourself up and ease yourself down.

Onoaida Onsen

Another highlight is Onoaida Onsen, just next to the trailhead. For ¥200 you can enjoy this hot spring favored by many locals.

Charcoal making:
Wood is left in the kiln for ten days.

The forest through which the trail winds is a great example of the low-altitude broadleaf evergreen forests Yakushima's inhabitants have traditionally depended on for their daily needs. You'll even pass an old charcoal kiln. Keep your eyes open, and you may spot plants including orchids and balanaphors. There are also quite a few streams along the way, but don't expect them to be as pristine as water bubbling up in Yakushima's mountainous interior. The trail is a bit unclear in places where it has been eroded by typhoons or where trees have fallen down, so you'll also want to keep your eyes on those pink tape ribbons so you don't get lost!

When you get to the open shelter at the fork, make sure to turn left instead of heading up into the mountainous interior. No matter what the Lonely Planet says, that's a long, long hike better attempted in the reverse direction. Needless to say, that's exactly the route I decided to do on my first oh-so-clueless visit to Yakushima, and while I had a good time and I came out alive, I highly encourage everyone to plan a little bit better than me.

After the fork, there are a couple beautiful little river that you'll cross. (Oh yeah I wouldn't recommend this trail in bad weather, because you'll have to turn back if they are overflowing.)

And shortly after that you'll reach the destination. Hopefully you've brought lunch!

Final Elevation: ~500m
Trail Head Elevation: ~100m
Map time: 3.5 hours (About 7.5 km) round trip. I recommend 4 hours for this trip.
Bus stop: Onoaida (Follow the signs to Onoaida Onsen)

View Ja no Guchi Waterfall in a larger map