Amorphophallus titanum, the titan arum, is a flowering plant with the largest unbranched inflorescence in the world. The talipot palm, Corypha umbraculifera, has a larger inflorescence, but it is branched rather than unbranched. A. titanum is endemic to Sumatra.
Due to its odor, like that of a rotting corpse, the titan arum is characterized as a carrion flower, and is also known as the corpse flower or corpse plant (Indonesian: bunga bangkai—bunga means flower, while bangkai can be translated as corpse, cadaver, or carrion). The titan arum’s berries arrange in a regular cylindrical form that resemble the packing of spheres inside a cylindrical confinement. Those structures are also called columnar structures or crystals.
Amorphophallus titanum derives its name from Ancient Greek (άμορφος – amorphos, “without form, misshapen” + φαλλός – phallos, “phallus”, and titan, “giant”). The popular name “titan arum” was coined by W.H. Hodge.
The titan arum’s inflorescence can reach over 3 metres (10 ft) in height. Like the related cuckoo pint and calla lily, it consists of a fragrant spadix of flowers wrapped by a spathe, which looks like a large petal. In the case of the titan arum, the spathe is a deep green on the outside and dark burgundy red on the inside, with a deeply furrowed texture. The spadix is hollow and resembles a large baguette. Near the bottom of the spadix, hidden from view inside the sheath of the spathe, the spadix bears two rings of small flowers.
The upper ring bears the male flowers, the lower ring is spangled with bright red-orange carpels. The “fragrance” of the titan arum resembles rotting meat, attracting carrion-eating beetles and flesh flies (family Sarcophagidae) that pollinate it. The inflorescence’s deep red color and texture contribute to the illusion that the spathe is a piece of meat.
During bloom, the tip of the spadix is approximately human body temperature, which helps the perfume volatilize; this heat is also believed to assist in the illusion that attracts carcass-eating insects.
Both male and female flowers grow in the same inflorescence. The female flowers open first, then a day or two following, the male flowers open. This usually prevents the flower from self-pollinating.
After the flower dies back, a single leaf, which reaches the size of a small tree, grows from the underground corm. The leaf grows on a somewhat green stalk that branches into three sections at the top, each containing many leaflets. The leaf structure can reach up to 6 m (20 ft) tall and 5 m (16 ft) across. Each year, the old leaf dies and a new one grows in its place. When the corm has stored enough energy, it becomes dormant for about four months. Then the process repeats.
The corm is the largest known, typically weighing around 50 kg (110 lb). When a specimen at the Princess of Wales Conservatory, Kew Gardens, was repotted after its dormant period, the weight was recorded as 91 kg (201 lb).
In 2006, a corm in the Botanical Garden of Bonn, Germany was recorded at 117 kg (258 lb), and an A. titanum grown in Gilford, New Hampshire by Dr. Louis Ricciardiello in 2010 weighed 138 kg (305 lb).
However, the current record is held by a corm grown at the Royal Botanic Garden Edinburgh, weighing 153.9 kg (339 lb) after 7 years’ growth from an initial corm the size of an orange.
Amorphophallus titanum is native solely to western Sumatra, where it grows in openings in rainforests on limestone hills. However, the plant is cultivated by botanical gardens and private collectors around the world.
The titan arum grows in the wild only in the equatorial rainforests of Sumatra, Indonesia. It was first scientifically described in 1878 by Italian botanist Odoardo Beccari. The plant flowers only infrequently in the wild. It first flowered in cultivation at the Royal Botanic Gardens, Kew, London, UK in 1889, with over one hundred cultivated blossoms since then. The first documented flowerings in the United States were at the New York Botanical Garden in 1937 and 1939.
This flowering also inspired the designation of the titan arum as the official flower of the Bronx in 1939, only to be replaced in 2000 by the day lily. The number of cultivated plants has increased in recent years, and it is not uncommon for there to be five or more flowering events in gardens around the world in a single year.
Advanced pollination techniques mean that this plant is rarely cultivated by amateur gardeners. However, in 2011, Roseville High School (Roseville, California) became the first high school in the world to bring a titan arum to bloom.
In 2003, the tallest bloom in cultivation, some 2.74 m (9 ft 0 in) high, was achieved at the Botanical Garden of the University of Bonn in Germany. The event was acknowledged by Guinness World Records.
In 2005 this record was broken at the botanical and zoological garden Wilhelma in Stuttgart, Germany; the bloom reached a height of 2.94 m (9 ft 8 in). The record was broken again by Louis Ricciardiello, whose specimen measured 3.1 m (10 ft 2 in) tall in 2010, when it was on display at Winnipesaukee Orchids in Gilford, New Hampshire, US. This event, too, was acknowledged by Guinness World Records.
In cultivation, the titan arum generally requires 7 to 10 years of vegetative growth before blooming for the first time. After its initial blooming, there can be considerable variation in blooming frequency. Some plants may not bloom again for another 7 to 10 years while others may bloom every two to three years. A plant has been flowering every second year (2014,16, 18 and 2020) in the Botanical Garden in Copenhagen.
There have also been documented cases of back-to-back blooms occurring within a year and corms simultaneously sending up both a leaf (or two) and an inflorescence. There has also been an occasion when a corm produced multiple simultaneous blooms.
The spathe generally begins to open between mid-afternoon and late evening and remains open all night. At this time, the female flowers are receptive to pollination. Although most spathes begin to wilt within twelve hours, some have been known to remain open for 24 to 48 hours. As the spathe wilts, the female flowers lose receptivity to pollination.
Self-pollination was once considered impossible, but in 1999, Huntington Botanical Garden botanists hand-pollinated their plant with its own pollen from ground-up male flowers. The procedure was successful, resulting in fruit and ten fertile seeds from which several seedlings were eventually produced. Additionally, a titan arum at Gustavus Adolphus College, in Minnesota, unexpectedly produced viable seed through self-pollination in 2011.
As the spathe gradually opens, the spadix releases powerful odors to attract pollinators, insects which feed on dead animals or lay their eggs in rotting meat. The potency of the odor gradually increases from late evening until the middle of the night, when carrion beetles and flesh flies are active as pollinators, then tapers off towards morning.
Analyses of chemicals released by the spadix show the stench includes dimethyl trisulfide (like limburger cheese), dimethyl disulfide, trimethylamine (rotting fish), isovaleric acid (sweaty socks), benzyl alcohol (sweet floral scent), phenol (like Chloraseptic), and indole (like feces).