Amorphophallus titanum - The titan arum

Amorphophallus titanum, the titan arum, is a flowering plant in the family Araceae. It has the largest unbranched inflorescence in the world. The inflorescence of the talipot palm, Corypha umbraculifera, is larger, but it is branched rather than unbranched. A. titanum is endemic to rainforests on the Indonesian island of Sumatra.

Because its flower blooms infrequently and only for a short period, it gives off a powerful scent to help attract pollinators quickly and effectively. The strong odor it emits resembles that of rotting flesh; hence it is characterized as a carrion flower and is also known as the corpse flower or corpse plant, as translated from the original Indonesian word 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 resembles the packing of spheres inside a cylindrical confinement. Those structures are also called columnar structures or crystals.

Etymology

A. titanum derives its name from Ancient Greek (ἄμορφος amorphos, "without form, misshapen" + φαλλός phallos, "phallus", and Τιτάν Titan, "titan, giant").

Description

Its 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. The tallest documented inflorescence was recorded at Meise Botanic Garden on 13 August 2024 and reached 322.5 cm.

The titan arum's inflorescence can reach over 3 m (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 almost 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 odor ("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 roughly 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 resembles a small tree and reaches a similar size, grows from the underground corm. The leaf grows on a patterned green and white 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. The stalk, or petiole bearing the leaf can be up to 15-16 inches (38-41 centimeters) thick at soil level and still 12-13 inches (30–32 cm) at breast height (D.B.H.). 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.

Distribution

A. 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.

Cultivation

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 100 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. In the Botanical Gardens of Bonn, the titan arum was cultivated since 1932, and the largest collection was built up by Wilhelm Barthlott after 1988; about 30 flowers were recorded and researched since. The number of cultivated plants has increased in recent years, and not uncommonly five or more flowering events occur in gardens around the world in a single year, since today the cultivation requirements for gardens are known in detail. Challenging cultivation constraints 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 May 2003, the tallest inflorescence in cultivation, some 3.20 m (10 ft 5 in) high (measured from its corm, 3.07 m from the soil surface), was grown at the Botanical Garden Bonn in Germany; this record was analyzed, photographed, and documented in detail. The event was acknowledged by Guinness World Records. The largest flower in the USA by Louis Ricciardiello, measured 3.10 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.

Blooming

In cultivation, the titan arum generally requires five to ten years of vegetative growth before blooming for the first time. After a plant's initial blooming, there can be considerable variation in its blooming frequency. The cultivation conditions are known in detail. Some plants may not bloom again for another seven to ten years, while others may bloom every two or three years. At the botanical gardens in Bonn, under optimal cultivation conditions, the plants flowered every other year. A plant has also been flowering every second year (2012 to 2022) in the Copenhagen Botanical Garden. Consecutive blooms occurring within a year have been documented and corms simultaneously sending up both a leaf (or two) and an inflorescence. There has also been an occasion when a 117 kilograms (258 lb) corm produced three simultaneous blooms in Bonn, Germany. There was also a triplet bloom at the Chicago Botanic Garden in May 2020 named "The Velvet Queen", but viewing was closed to the public due to COVID-19.

The spathe generally begins to open between midafternoon 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 12 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 1992, botanists in Bonn hand-pollinated their plant with its own pollen from ground-up male flowers. The procedure was successful, resulting in fruit and hundreds of seeds from which numerous seedlings were eventually produced and distributed. 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 heats up to 37°C (99 °F), and rhythmically 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 (garlic), trimethylamine (rotting fish), isovaleric acid (sweaty socks), benzyl alcohol (sweet floral scent), phenol (like Chloraseptic), and indole (like feces).