SURAT THANI - A new species of tree has been discovered in the southern province of Surat Thani by a team of Thai researchers led by Dr Chatthida Wiya, a plant taxonomist from the Botanical Garden Organization.
The discovery was made in collaboration with researchers from Chiang Mai and Kasetsart universities, the Department of National Parks, Wildlife and Plant Conservation, and the Department of Agricultural Extension. The findings were published in the international journal Plant Systematics and Evolution (Vol 311, Issue 3) on May 1, 2025.
(Photo: the Botanical Garden Organization)
The tree, named “Tharathum” in Thai — from thara meaning water and thum meaning tree — belongs to the Annonaceae family and the genus Sageraea. Its scientific name is Sageraea multiovulata Wiya, Sinbumr. & Chaowasku, incorporating the names of the researchers who discovered it.
Tharathum is a medium-sized tree that can grow up to 18 metres tall. It features cream to pale yellow flowers and produces large cluster fruits that turn yellowish-green when ripe. The seeds, arranged in two rows, are notably numerous — with each ovary containing 19–20 ovules, the highest number ever recorded in the genus, which typically has only 5–12, the researchers said.
(Photo: the Botanical Garden Organization)
What makes Tharathum especially unique is its habitat. It grows near the Tapi River in Khian Sa district of Surat Thani, where the area is submerged for about six months each year. The fruit ripens at the start of the flood season around October, suggesting the river current helps disperse the seeds, while prolonged submersion soften the fruit for easier decomposition.
The species is currently classified as Critically Endangered due to its extremely limited range. It has only been found in a single wetland area surrounded by oil palm and rubber plantations. Conservation efforts are being supported by the local community.
(Photo: the Botanical Garden Organization)
The Botanical Garden Organization has received Tharathum saplings from the researchers and is now cultivating them at the Queen Sirikit Botanic Garden in Chiang Mai as part of a conservation programme.
While no commercial uses have yet been reported, researchers believe further study could uncover valuable compounds and help support sustainable conservation through economic incentives.