The world's largest flower, a three foot-wide bloom that smells like rotting flesh, is related to sweet-smelling posies, researchers say. The flower, which is one of 20 species collectively called Rafflesia, is related to poinsettias, violets, passionflowers, and other members of the order Malpighiales, according to a paper published in the current Proceedings of the National Academy of Sciences. Researchers also have some intriguing theories as to why Rafflesia smells so awful, why its flowers bloom only once a year and live for five to seven days, why the plant is a parasite, and why it likes to attract flies that normally go for mounds of dead flesh. While Rafflesia would not make a very appealing Valentine's Day bouquet, it has intrigued plant specialists for years due to its rarity and size. The flower inspired Todd Barkman, assistant professor of biological sciences at Western Michigan University, and colleagues to analyze Rafflesia's phylogeny. Rafflesia is a parasitic plant that lacks roots, stems, and leaves. Usually botanists trace plant orders using chloroplast cells, but since Rafflesia does not have them, Barkman and his team instead analyzed the Rafflesia's mitochondrial DNA (mtDNA), which corresponds to chloroplast cells.

The mtDNA studies revealed that the large, stinky flower is related to more normal-sized, pleasantly fragrant posies. Despite its enormity, Rafflesia does resemble passionflowers, according to Barkman. Both have their stamens and pistils fused together in a central column, and both produce a corona, or crown, in the shape of a ring.


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