Volume 123/27 2012
Posted: December 6, 2012
Pandanus helicopus Kurz.

Pandanus helicopus. This tree-like, erect pandan can grow to 6 m tall, usually standing in water with the lower part of the trunk and roots submerged. The bark is beset with short spines, while the leaves have noticeable orange-brown bases and purple teeth. The seldom seen inflorescence is creamy yellow and is protected by bright yellow leaf-like bracts. The infructescence is a large, oblong aggregate fruit made up of many tightly compressed fruitlets which change from green to warm brown when ripe, and due to its heavy weight it hangs pendent on a zigzag peduncle from the centre of the leaf rosette. As the tree becomes top-heavy with leaves, branches and fruit, the many thick prop roots provide support in the usually soft peaty substrate. These combinations of characters make identifying this freshwater swamp species relatively easy.

Locally known as rassau, it is extremely common in Tasik Bera and Tasik Chini where it forms monotonous, tall and dense thickets along the edge of open waters, which can form a few metres-wide border to a wide zone choking the lake and causing obstruction to boat passage. Together with the Lepironia reed beds, rassau swamp forms the second largest microhabitat type in Tasik Bera, covering more than 30% of the total lake area. Sometimes burnt rassau patches can be seen – the result of local communities wanting to clear waterways for their boats or to flush out the freshwater terrapins and turtles that take refuge among the tangle of roots, which are prized as local delicacies. Despite this periodic burning, rassau exhibits the fast growing traits of pioneer species and continues to dominate the two freshwater lakes. Elsewhere, rassau can be found in riparian forest and river backwaters mainly in the state of Pahang and Johor.
By: Chew Ming Yee (chew@frim.gov.my)
Edited by: Dr. Ruth Kiew



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