Titan arum (Amorphophallus titanum)
|Size||Leaf height: up to 7 m (2)|
Spathe circumference: up to 3 m (3)
Inflorescence height: 2 m (2)
Tuber weight: up to 75 kg (2)
Classified as Vulnerable (VU) on the 1997 IUCN Red List of Threatened Plants (1).
The spectacular titan arum produces the world’s largest compound flower or inflorescence; the largest of which is reported to have reached 3.5 metres tall (2). Years may pass between flowering events but when the time does come this plant produces a truly spectacular bloom. A large bud appears on the forest floor and with remarkable speed the flower grows and opens to its full size (4). As with all members of the Arum family the inflorescence consists of a petal-like structure known as a ‘spathe’ and a flower-bearing spike, the ‘spadix’; the whole structure is borne on a stout stalk only 25 – 35 cm high (2). The spathe resembles an upturned bell with a frilly margin, the outside is pale green but when it unfurls the inner crimson walls are displayed (3). The spadix emerges above the spathe, the upper portion is known as the appendix and is brownish-yellow in colour. The male and female flowers are situated on the lower portions of the spadix where they are sheltered by the giant spathe. The tightly packed cream male flowers are found in a band above the female flowers (2). Once pollinated, the female flowers develop into olive-sized bright red fruits that are carried in cylindrical clusters up to half a metre long (2). The single leaf of the titan arum is also gigantic in size; resembling a small tree rather than a leaf, it can tower up to 5 metres tall and divides into an umbrella-like canopy that can be 7 metres across (2).
Endemic to Sumatra in the Indonesian archipelago (5).
The titan arum dwells in the rainforests of western Sumatra, on steep hillsides that are 120 – 365 metres above sea level (2).
The giant leaves and flowers of the titan arum are produced from an equally enormous tuber that lies under the rainforest soil, and acts as a food storage organ (4). Each year the leaf dies back before a new one develops but eventually the inflorescence begins to emerge in its place, growing at an amazing 10 cm a day (3). Once the spathe has unfurled in all its glory the female flowers are ready to receive pollinators. The spadix heats up emitting a putrid stench that has lead to the Indonesian name for this flower of ‘bunga bangkai’ or ‘corpse flower’ (2). It is thought that the smell helps to attract carrion beetles or sweat bees from far away; once inside the welcoming spathe they are trapped, unable to scale the smooth walls or the bulge in the spadix that tops the flowers. Male flowers release their pollen the next day and the appendix of the spadix begins to wither, thus allowing the insects to escape, brushing through the pollen on their way (2). This mechanism of consecutive flowering means that self-fertilisation is prevented (5).
After flowering, the enormous spathe petal collapses and twists around the base of the spadix, protecting the developing fruit within. As the fruits ripen, the spathe completely rots away leaving the bright red berries on display to be eaten, and therefore dispersed, by rainforest birds such as hornbills (2).
The rainforests of Sumatra are under massive threat of deforestation, as vast areas are logged for timber and to make way for palm plantations. It is estimated that Indonesia has now lost around 72% of its original rainforest cover and the scale of deforestation is continuing at an alarming rate (6). As well as affecting titan arum numbers directly, the loss of habitat is also endangering species such as the rhinoceros hornbill (Buceros rhinoceros), which is an important seed distributor (6).
The Royal Botanic Gardens, Sydney and Bogor Botanic Gardens, Indonesia have been working together on conservation techniques for this rainforest giant. As well as investigating propagation techniques, surveys of wild plants have been undertaken and educational materials produced (7). This plant has previously proved very difficult to grow in cultivation; ongoing research may provide the key to the continued survival of this spectacular member of the plant kingdom.
For further information on the titan arum, visit:
Royal Botanic Gardens, Kew
BBC Wildlife Finder:
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- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Inflorescence: the reproductive shoot of the plant, which bears flowers (See http://www.rbgkew.org.uk/ksheets/pdfs/flower.pdf for a fact sheet on flower structure).
- Walter, K.S. & Gillett, H.J. [eds] (1998) 1997 IUCN Red List of Threatened Plants. Compiled by the World Conservation Monitoring Center. IUCN – The World Conservation Union, Gland, Switzerland and Cambridge, UK.
- Brown, D. (2000) Aroids: plant of the Arum family. [2nd edn] Timber Press, Oregon.
Royal Botanic Gardens, Kew (August, 2003)
- Attenborough, D. (1995) The Private Life of Plants. BBC Books, London.
The Huntington Library, Art Collections and Botanical Gardens (August, 2003)
Wisconsin University (August, 2003)
Royal Botanic Gardens, Sydney (August, 2003)