Amorphophallus titanum (titan arum)
Titan arum is a giant among plants, with a massive flowering structure that rises some three metres above the ground. Its flowering is rare and unpredictable, and always grabs the headlines.
Amorphophallus titanum (Becc.) Becc.
Common name: titan arum, corpse flower
Conservation status: Classified as Vulnerable (V) in the 1997 IUCN Red List of Threatened Plants.
Key Uses: Ornamental.
Known hazards: Emits a nauseating smell on flowering.
About this species
Titan arum produces one of the largest flowering structures and one of the foulest odours in the plant kingdom. With its huge flowering structure rising up to three metres above the ground, and its single immense leaf, it certainly is a giant among plants, as its name suggests. The plant flowers only rarely.
Conophallus titanum Becc., Amorphophallus selebicus Nakai
Geography and distribution
Amorphophallus titanum is restricted to Sumatra in the Indonesian archipelago.
It is found growing in the rainforests of western Sumatra, on steep hillsides, at 120 to 365 m above sea level.
Description: Titan arum inflorescence
Flowers: Titan arum has a massive inflorescence (flowering structure) consisting of a spathe (collar-like structure) wrapped around a spadix (flower-bearing spike). The spathe is the shape of an upturned bell. It is green speckled with cream on the outside, and rich crimson on the inside. It has ribbed sides and a frilled edge, and can be up to three metres in circumference. The flowers are carried on the lower end of the greyish-yellow spadix. At the base of the spadix, within the protective chamber formed by the spathe, is a band of cream male flowers above a ring of the larger pink female flowers. When the flowers are ready for pollination, the spadix heats up and emits a nauseating smell. This stench is so bad that the Indonesians call the plant ‘the corpse flower’.
Tuber: The inflorescence rises from a tuber, a swollen underground stem modified to store food for the plant. This tuber, more or less spherical in shape and weighing 70 kg or more, is the largest such structure known in the plant kingdom.
Leaf: After flowering, the inflorescence dies back and in its place a single leaf emerges. Reaching the size of a small tree, up to 7 m tall and 7 m across, the leaf consists of a sturdy glossy green stalk mottled with cream, which divides into three at its apex and bears numerous leaflets. Sugars made in the leaf are transported back to the tuber for storage as starch. Each year, the leaf withers before a new one develops, using the tuber’s energy stores. When the plant is ready to flower again, the tuber becomes dormant for up to four months before another inflorescence emerges, growing upwards at a rate of some 10 cm per day.
Pollination: Despite huge interest in titan arum, there has been no proper scientific study of its pollination to date. What is thought to occur is that when the flowers are ready for pollination the pollen-carrying insect enters, dives to the bottom of the inflorescence, deposits pollen on the stigmas and then stays there for 24 hours, emerging with the shedding of the pollen at around the same time the following day. Whether the insects are trapped or stay in the inflorescence because of some attraction remains to be verified, but the trap idea seems reasonable. The powerful foul smell and evening to night flowering suggests the pollinators may be beetles, or possibly flies which lay eggs in cadavers. The world expert on Amorphophallus, Wilbert Hetterscheid, has suggested it is likely that carrion beetles are the true pollinators.
Fruits: From the pollinated female flowers, the fruits develop inside the spathe chamber. Once they are ripe, the spathe withers completely exposing the bright scarlet fruits. These attract the attention of hornbills and other birds that eat them and disperse their seeds. The fruiting body looks rather like a giant version of the familiar lords and ladies (Arum maculatum) which appears in British hedgerows and woods in late summer. While A. titanum undeniably has the bulkiest inflorescence in the Araceae family, it is not the largest in terms of vertical size. That honour belongs to Amorphophallus gigas which has a similarly sized spathe and spadix carried on a 3 to 4 m peduncle. Perhaps even more remarkable is the recently described A. pusillus from Vietnam, which has an inflorescence just 3 cm tall.
Threats and conservation
The rainforests of Sumatra are under massive threat of deforestation, as vast areas are logged for timber and to make way for oil 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. 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.
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. 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.
Uses: Titan arum is used for ornamental displays and can be an immensely popular visitor attraction.
Cultivation: This species has proved very difficult to cultivate, and there are only a handful of places in the world that do so. Even under optimum conditions the plant takes about six years to flower from seed.
The Amorphophallus titanum is cultivated in a tropical glasshouse, under conditions of high temperature and humidity, and kept in the shade. A well-drained, organic compost is used and plants are fertilised regularly during the growing season. Plants should be kept dry when dormant and watered when a new leaf/ inflorescence first appears. A.titanum is prone to rotting if over-watered. Plants should be re-potted whilst in the dormant stage (quite a feat when older corms can weigh over 70 kg). For pollination to occur, two plants at the right stages of maturity are required (one with receptive female flowers and one at the stage where male flowers are releasing pollen). The fruits are bright red when mature.