Rafflesia arnoldii

Rafflesia arnoldii is a tropical parasitic plant native to Sumatra, Indonesia. Its reddish-brown flower has five large lobes marked with pale spots and can grow to roughly one metre across. The bloom lasts for only a short period, making it an unusual and difficult plant to observe in the wild. Kew describes it as the world's largest individual flower; the claim refers to a single flower, not a cluster of flowers.

Unlike most plants, Rafflesia arnoldii has no visible leaves, stems or roots. Its vegetative body consists of strands living inside Tetrastigma vines, from which it obtains water and nutrients. When ready to bloom, a cabbage-like bud emerges through the host vine's bark and develops into the conspicuous flower. Much of the plant's life cycle remains poorly understood, and its dependence on a specific host makes cultivation challenging.

The flower emits an odour resembling decaying meat. This attracts flies and other insects that visit carrion, which can carry pollen between flowers. The smell has given Rafflesia species the popular name corpse flower. That common name is also used for the unrelated titan arum (Amorphophallus titanum), whose large structure is an inflorescence made up of many small flowers rather than one giant flower.

Rafflesia arnoldii is part of a genus with substantial conservation concerns. A 2023 study reported that all 42 species then assessed in the genus were threatened under IUCN criteria, with habitat loss and the limited protection of known populations among key concerns. Those genus-wide findings should not be mistaken for an individual IUCN assessment of R. arnoldii: Kew lists this species as Not Evaluated. Protecting forest habitat and improving knowledge of the plants and their host vines are important conservation priorities.