The flowering of the Amorphophallus titanum (titan arum), at the Royal Botanic Garden Edinburgh in 2015 was a first for Scotland, when the corm was 13 years old.

Since that first flower we have had a second in 2017 and now a third in 2019 – our 17 year old corm showing an unusual persistence.

The species originates in Sumatra and famously has one of the largest flowering structures of any plant. Everything about Amorphophallus titanum is big. The inflorescence stands three metres tall, whilst the single leaf reaches a height of six metres and a spread of five metres and looks like a small tree rather than the herbaceous plant that it actually is. In 2003, when the Garden received the corm from Hortus Botanicus in Leiden, it was about the size of an orange, but by 2010 it weighed in at a record breaking 153.95 kg.

Amorphophallus titanum was first described to western audiences in 1878 by the Italian botanist Odoardo Beccari (1843-1920) and has been a botanical curiosity ever since. Amorphophallus titanum attracts pollinators through a pungent smell reminiscent of rotting flesh. It has recently been discovered that on two consecutive nights during flowering certain parts of the inflorescence heat up by 10ºC. This heating coincides with the opening of first the female and then the male flowers, and helps to spread the smell and attract the carrion flies and beetles that act as pollinators. This heating of the inflorescence, by a process called thermogenesis, is a feature of the arum family – Araceae. More familiar members of the family, that also heat up, are the native cuckoo pint or lords-and-ladies, Arum maculatum, and the popular houseplant known as the Swiss cheese plant, Monstera deliciosa.

Successfully bringing the Amorphophallus titanum to the point of flowering has involved replicating the conditions it would experience in the rain forest of Sumatra. The Wet Tropics House provides the required high humidity and temperatures. During the day, temperatures are between 22-25ºC, and by night above a minimum of 19ºC. The 1,000 litre pot is watered with a high potash liquid fertilizer, i.e. tomato fertilizer, and care is taken to avoid waterlogged conditions as this could cause the corm to rot. Often, an Amophophallus titanum will die after flowering, but with careful cultivation, a plant can continue to produce more leaves or flowers in subsequent years.

More work is needed to establish the conservation status ofAmorphophallus titanum in the wild. It is currently only known from the Bukit Barisan range of mountains in West Sumatra and is classified as endangered.

Sumatra is a part of the Garden’s ongoing research in Southeast Asia on diverse tropical plant families including the gingers (Zingiberaceae), begonias (Begoniaceae), Gesneriaceae, and tropical trees in the Sapotaceae and Malvaceae.