The Secret of the World’s Smelliest Flower

By Simon Cotton, University of Birmingham
July 9, 2015 Updated: July 13, 2015

By happy coincidence and far from its native home of western Sumatra in Indonesia, titan arum, the world’s smelliest bloom, flowered at Paignton Zoo in Devon, England, and at the Royal Botanic Gardens in Edinburgh, Scotland. It’s a rare event, but not to be outdone, in New York, Cornell University’s titan arum has also been showing off.

While in a recent study researchers identified the enzyme that plays a key role in producing the sweet fragrance found in roses, titan arum—or Amorphophallus titanum to give it its Latin name—is famed for a very different type of smell: that of rotting flesh. As one witness in Edinburgh put it, “At its peak in the glasshouse it actually made our eyes water.”

Related Coverage
The Secret of the World’s Smelliest FlowerWorld’s Tallest Flower

So what is this amazing plant, and why is it so smelly?

We Have the Victorians to Thank

The Victorian age was great for exploring. It was deep in present-day Tanzania in November 1871 that the American journalist Henry Morton Stanley uttered his famous (alleged) words: “Dr. Livingstone, I presume?” A few years later in 1878 in the rain-forests of Sumatra, a slightly less momentous, but much more unpleasant discovery was made, when a botanist from Florence, Italy, named Odoardo Beccari probably became the first Westerner to observe the smelliest plant in the world. He sent some seeds and tubers back home—from where some seeds made their way to Kew Gardens, London—and it was there in 1889 that Amorphophallus titanum flowered in the West for the first time. It actually also has a British relative, Arum maculatum, perhaps better known as the cuckoo pint.

Not quite so stinky. (Leonora Enking, CC BY-SA 2.0)
Titan arum, the world’s smelliest bloom. (Leonora Enking, CC BY-SA 2.0)

Cultivating Amorphophallus titanium isn’t a job for the impatient. It flowers irregularly, every few years. The plant has a vast underground tuber, which can weigh up to 75 kilograms (165 pounds) and produces a huge leaf, which can grow up to six meters (about 6.5 yards) tall. Sometimes it instead produces a huge inflorescence, stretching up to three meters high, with very small individual male and female flowers at the base, surrounded by a kind of giant green petal called a spathe. On average this only happens around every ten years. But when it does, you will certainly know about it, and they say that you can smell it from half a mile away.

A Master of Disguise

Its rotting flesh smell gives titan arum other alternative names such as the corpse flower or carrion plant. Its smell is designed to attract insects such as flies and carrion beetles, which normally feed on decaying flesh but will help pollinate it. The spathe is green on the outside but the flower head is red, so the plant looks like meat. This plant is really cunning—as it blooms it gives out quite a lot of heat, up to 36 degrees C (96 degrees F), which encourages the molecules to spread out by helping them vaporize, and also confirms the impression of “warm meat.” The insects crawl over the spathe to leave their eggs in what they believe to be rotten meat, transferring pollen and pollinating the plant in the process.

Some years ago, scientists at Kew Gardens identified the molecules responsible for these awful smells. The main ones are called dimethyl disulphide (DMDS) and dimethyl trisulphide (DMTS); they’ve been known in the laboratory for years, and yes, they do smell disgusting.

In Small Amounts

In small amounts, molecules such as DMDS and DMTS are an “off-flavor” in beer (DMDS is a byproduct of the fermentation process). The scientists looked at various species of the genus Amorphophallus (Araceae, the Arum family), including the titan arum, and found that most made DMDS and DMTS. Some also use other molecules such as organic acids like the ones found on “sweaty skin,” as well as indole, a molecule partly responsible for the smell of human feces. It’s not the only type of plant that smells like this. Scientists who examined the South African stinkhorn fungus (Clathrus archeri) discovered that it was producing DMDS just like a sample of rotten meat (and a dead rat).

'Dead horse arum' (Swallowtail Garden Seeds, CC BY 2.0)
‘Dead horse arum’ (Swallowtail Garden Seeds, CC BY 2.0)

Another arum (Helicodiceros muscivorus) found in Sardinia, Italy, and Corsica, France, is known as known as “dead-horse arum” (you can guess why). It uses dimethyl sulfide (DMS) as well as DMDS and DMTS to attract blowflies. Dimethyl sulphide is a molecule we’ve all smelt; it is part of the sulfur cycle and is responsible for the “smell of the seaside.” DMS is also the molecule that pigs and dogs look for when they detect black truffles underground in some parts of France. DMDS and DMTS are associated with the smell of Italian white truffles.

So Amorphophallus titanum isn’t what most people have in mind when they “say it with flowers.” Those flowers use a cornucopia of molecules with amazing smells to lighten our day and bring forth emotions that words cannot.The Conversation

Simon Cotton is a senior lecturer in chemistry at the University of Birmingham in the U.K. This article was previously published on TheConversation.com 

RECOMMENDED