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flower

The largest flower: the corpse flower

Before discussing the largest flower, we have to decide what we mean by “flower,” because what the ordinary person calls a flower is somewhat different from the botanists' definition.

Plants in the Family Asteraceae (Compositae), for example, which contains more species than most families, have flowers that are actually composed of dozens or hundreds of tiny individual flowers (florets), each with a pistil (the female part) and often with stamens (the male part) as well.

A single sunflower blossom, for example, consists of a ring of florets containing pistils, while florets in the center area have both pistil and stamen. So, to the botanist, the sunflower blossom is large, but the sunflower flowers are small.

By the botanists’ definition, the largest flower is that of Rafflesia arnoldii, whose blooms are about a meter (a yard) in diameter. It grows in Sumatra and Borneo. A gallery of photographs of this flower is at www.parasiticplants.siu.edu/Rafflesiaceae/index.html

The Rafflesia are a strange group of about 16 species, all parasitic plants that grow in the forests of Southeast Asia. They have no leaves, roots or stems, living off a host that is a vine. All are endangered.

Another, unrelated, giant corpse flower

By the layman's definition of a flower, the largest flower is the titan arum or corpse flower (Amorphophallus titanum), which is actually composed of hundreds of tiny flowers that form a central spadix. The confirmed record for size appears to be held by a plant at the Botanical Garden of the University of Bonn, Germany, whose spadix was 274 centimeters tall (about 9 feet), measured from soil level. A gallery of photographs showing the blooming of the record inflorescence is at www.botgart.uni-bonn.de/titangal/gal2003.html

Unlike Rafflesia, which are extremely difficult or impossible to grow, the titan arum can be viewed at a number of conservatories, especially since in 1993 a television production, The Private Life of Flowers, encouraged by Dr. James Symon, very kindly distributed seeds. In North America and Europe large crowds attend the brief blooming period (usually 2 days, at most 4).

• Botanical Conservatory, University of California, Davis, CA
• Botanische Gärten der Rheinische Friedrich-Wilhelms-Universität, Bonn, Germany
• Fairchild Tropical Garden, Miami, FL
• Fullerton Arboretum, Fullerton, CA
• Huntington Botanical Gardens, San Marino, CA (LA area)
• Marie Selby Botanical Gardens, Sarasota, FL
• New York Botanical Gardens, New York, NY
• Royal Botanical Garden, Kew, England
• United States National Botanical Garden, Washington, DC
• University of Wisconsin-Madison Botany Greenhouse, Madison, WI

(Anyone who knows of other conservatories showing the titan arum, please drop us a note.)

Why so big?

Curiously, the flowers of both Rafflesia arnoldi and Amorphophallus titanum appear very briefly (a few days at most), and both smell like carrion. They are pollinated by carrion flies. Charles Davis has speculated that, at least in the case of the Rafflesia, the large size is adaptive because carrion flies prefer larger corpses.

Charles C. Davis, Maribeth Latvis, Daniel L. Nickrent, Kenneth J. Wurdack and David A. Baum.
Floral Gigantism in Rafflesiaceae
Science, vol. 315, issue 5820, pages 1812 (30 Mar 2007)
doi: 10.1126/science.1135260
Davis's speculation is in a quotation in Harvard Magazine, March-April 2017, page 75.

resources

A good account of Rafflesia: www.kew.org/science-conservation/plants-fungi/rafflesia-arnoldii-corpse-flower

A comprehensive page about the titan arum, from the International Aroid Society: www.aroid.org/genera/speciespage.php?genus=amorphophallus&species=titanum

An article by Doug Johnson, Can This Group Revive the Finicky Corpse Flower?

A movie from the BBC showing Rafflesia arnoldii opening: www.arkive.org/species/GES/plants_and_algae/Rafflesia_spp/Rafflesia_spp_01.html

The smallest flower

Were the first flowers big or little?

The answer, of course, is sex: sex endlessly churning chromosomes and creating new combinations of the inheritable characteristics of individual organisms. Passive pollination by wind and water can take one only so farco-evolution of flowers and pollinatords. and even garden club propagators. A host of specialized strtcures as flowers evolved, they developed

until its value became apparent (in the form of higher numbers of fertile offspring,

Peter K. Endress.
The flowers in extant basal angiosperms and inferences on ancestral flowers.
International Journal of Plant Sciences, vol 162, no 5, pages 1111-1140 (2001).

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Last revised: 18 August 2020.