Rafflesia kerrii Meijer, Thailand's largest flower

ABSTRACT: With flowers more than 70 cm in diameter, Rafflesia kerrii Meijer is Thailand's largest flower. It was first collected by A.F.G. Kerr in 1927 and described by Willem Meijer in 1984. In 1989, I studied fresh specimens from southern Thailand and was able to confirm its status as a distinct species. Here, I present a description of the plant in greater detail than previously reported. It is distinguished from other rafflesias by having very small warts on the perigone lobes. It is parasitic on the roots of lianas including Tetrastigma leucostaphylum (Dennst.) Alston ex. Mabberly (Vitaceae) and T. papillosum (Bl.) Planch. Flowers are unisexual and pollination is probably carried out by flies. The means of seed dispersal is unknown. R. kerrii is confined to the southern Tenasserim Hills in the provinces of Chumpon, Ranong and Surat Thani. Its status is "vulnerable" according to IUCN Red Data Book criteria. Threats to its survival include habitat destruction and over-collection. I suggest that R. kerrii be promoted as a tourist attraction, to provide an economic incentive for local people to protect the species.