Amorphophallus Titanum, the World’s Smelliest Plant

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The rainforest plant Amorphophallus titanum, also known as the titan arum, lays claim to the dubious title of the world’s smelliest plant. But there’s more to it than just the smell of rotting flesh – it also produces what’s probably the world’s largest bloom in a short but spectacular flowering which regularly attracts many curious onlookers to the few botanical gardens where it is cultivated.

The World’s Largest Bloom

The titan arum grows from a corm and takes around ten years to reach flowering maturity. Made up of male and female flowers protected by a leaf-like wrapping called a spathe, the enormous central structure can reach over three metres in height. According to Dr Max Coleman of Edinburgh’s Royal Botanical Gardens, this makes A. titanum probably the largest bloom in the world (interview conducted 1 June, 2011).

Although the flowers themselves are concealed within the spathe, during the short period of flowering the collar-like structure unfurls, giving the plant the appearance of a single flower, green on the outside and red on the inside.  The whole structure can be up to three meters in diameter, as wide as it is tall. The flower spike later bears a profusion of red berries.

The sheer scale of the plant is staggering: in Edinburgh, the corm required a 750 liter pot; even large botanical gardens may struggle to find space for it. Getting from a corm, albeit a large one, to such an enormous plant over a relatively short period of time (typically a couple of months) requires a huge rate of growth – as much as 10cm or more during the later stages.

Why Amorphophallus Titanum is the World’s Smelliest Flower

As if being the largest bloom in the world wasn’t enough, A. titanum also lays claim to the title of the world’s smelliest – giving it the alternative name of ‘corpse flower’. During its (mercifully short) flowering period the smell can be detected by humans at a distance of around half a mile, and by insects at considerably greater distances.

It is, of course, the insects which are crucial, because A. titanum uses its ‘dead-meat’ aroma as other flowering plants use more pleasant fragrances – to attract potential pollinating insects which are drawn to the smell, becoming trapped inside the bloom. The odor is caused by a mix of gases emitted by the heating up of parts of the central flower spike, or spadix, by around 10⁰C, during two phases, (both of which occur at night).

Dr. Coleman describes a process in which the plant effectively traps the insects for the duration of the pollinating process. During the first phase, the female flowers are ready for pollination and the insects deposit pollen which they have brought in from other A titanium plants. During the second phase the following night, they collect pollen from the male flowers and, as the spathe rapidly dies back, are released to go and pollinate elsewhere.

The titan arum produces attractive red berries: Image by Don Mcauley

Risks and Threats

A. titanum is rare and has a limited range. Discovered in 1878 in the Sumatran rainforest, it is at risk from deforestation in the relatively small area where it occurs naturally. Although it is becoming more closely studied its biology is not yet clearly understood, most particularly in terms of the detail of the pollination process (Korotkova and Barthlot).

Pollination of cultivated plants is undertaken by hand, using pollen often gathered from plants on different continents.  The cultivation of A. titanum in botanical gardens such as Edinburgh is important not only in maintaining the survival of the species, but also in increasing understanding of its complex biology – as well as providing a memorable experience for visitors lucky enough to see it.

Sources
Nadja Korotkova and Wilhelm Barthlot.  “On the thermogenesis of the Titan arum (Amorphophallus titanum)” Plant Signalling and Biology 2009. Accessed 2 June 2011.
Royal Botanic Gardens, Edinburgh. “Amorphophallus titanum (titan arum) Frequently asked questions.” Accessed 2 June 2011.
Royal Botanical Gardens, Kew. “Species information, Amorphophallus titanum.” Accessed 2 June 2011.
W Barthlot et al. “A torch in the rain forest: thermogenesis of the Titan arum (Amorphophallus titanum).” Nees Institute for Biodiversity of Plants. Accessed 2 June 2011

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