The Sumatran native Amorphophallus titanum (titan arum) was a soaring success for the botanic garden when it flowered in June 2015, for the first time in Scotland, attracting around 19,000 visitors.
So far this time, 13,754 people have already been through the Glasshouse to see the plant and more were expected this weekend. Its flowering is rare and unpredictable.
The plant is known as the "corpse flower’’ because it emits a stench like rotting flesh to attract pollinating insects. Now in full bloom, the plant is continuing to grow and latest measurements reveal it grew three centimetres in 24 hours.
The titan arum typically grows 3 metres above the ground and a single leaf can reach a height of six metres and a spread of five metres.
World expert Dr Inayat Olmedo, who flew in specially from Basel in Switzerland, just hours before the flower began to open, said: "We needed to make sure the parameters were just right for cutting the hole to expose the female flowers for pollination. We had to be very careful not to damage the plant.’’
The special resident is not only good for driving visitor numbers. Scientists at RBGE are studying the Amorphophallus titanum to find out more about its pungent small and what pollinators it attracts.
RBGE tropical botanist Dr Peter Wilkie said: "The last time the Amorphophallus titanum flowered we studied its morphology and structure, this time we want to better understand its biology. We want to investigate how it produces its famous smell, what pollinators are attracted to the smell and what animals disperse its seed. We are also keen to investigate why several plants are flowering in different parts of the world at the same time - are there particular environmental triggers? Are the plants that flower at the same time very closely related genetically? For such an iconic plant there is so much we don’t yet know."
The plant only grows only on the Indonesian island of Sumatra, and its success in RBGE is a result of the research focus it has on the Indonesian island. It has 440 more species from Indonesia in its glasshouses.
To successfully bring the titan arum to the point of flowering The Lowland Tropics House was kept at a minimum of 19 degrees and between 21-25 degrees during the day. Its 1,000 litre pot is watered with a high potash liquid fertiliser and care is taken to avoid waterlogged conditions as this could cause the corm to rot.
The plant corm was gifted to RBGE in 2003 by Hortus Botanicus in Leiden, Netherlands, when it was the size of an orange. In 2010 staff borrowed scales from Edinburgh Zoo to weigh the corm, finding it was a record-breaking £153.9kgs. The previous world record was 117kgs, held by Bonn Botanic Gardens, Germany.
A second titan arum at The Eden Project has since been grown from pollen harvested in Edinburgh by Wilkie.
The titan is currently only known to grow in the Bukit Barisan range of mountains in West Sumatra and is classified as Vulnerable (V) on the 1997 International Union for Conservation of Nature (IUCN) Red List of Threatened Plants.