Our trip to Hutan Lipur Lata Tembakah, Terengganu, in May 2019 was unforgettable. Not only because of its mesmerizing waterfall, but the mass flowering event of trees in the Dipterocarpaceae family made it so worthwhile to travel the approximately 500 km from Kuala Lumpur to Jerteh for the field work. Many trees of Dipterocarpus spp. and Shorea spp. were flowering and fruiting during our visit. The forest floor was naturally adorned with the creamy and slightly pink petals of aborted dipterocarp flowers.

One species that was flowering heavily and fruiting was Dipterocarpus grandiflorus. The epithet grandiflorus literally means “large flower” in reference to the size of the flowers. The ridge on its calyx tube resembles the shape of a star fruit or Averrhoa carambola, which in Malay is called “belimbing” (Symington et al., 2004). Thus, its vernacular name Keruing belimbing, Keruing being the Malay name for Dipterocarpus spp.

Dipterocarpus grandiflorus is an emergent tree that can grow up to 45 m tall and 1.5 m in diameter. Trees in the Dipterocarpaceae family are known as “dammar group trees” and like all trees in the dammar group, its stem produces resin. It has leaves which are thick, glabrous (hairless) and leather-like in texture. The leaf also has a long petiole, about 9 cm long and at least 2 mm in diameter. The flower is whitish or yellowish pink and the bud is 3.5 X 1.3 cm in size. Generally, Dipterocarpus spp. flower buds range in size from 1.5 X 0.5 to 6 X 2 cm (Ashton et al., 2004). Dipterocarpus grandiflorus also produces winged fruits that are among the largest in the genus. The calyx tube is about 7 X 3.5 cm, with two major wings of about 22 X 3 cm and another three shorter calyx lobes of about 1.5 cm long (Ashton et al., 2004). The dark purple young leaves and twigs with purple pink stipules are among physical characteristics that can be used for identification of this species.

This species has a wide distribution, from the Andaman Islands, Vietnam, Myanmar, Thailand, the Philippines, Indonesia, Malaysia to Singapore. In Malaysia, this species can be found in almost every state except Sarawak (Ashton et. al, 2004; Chua et al., 2010).

In Malaysia, the trade name for Dipterocarpus spp. timber is Keruing. The timber is also sold under the name Apitong and Panang in the Philippines, Gurjun in Burma, Eng in India and England, Hora in Ceylon and Yang in Siam (Gerry, 1952; Symington ,2004). Keruing is categorised as a medium hardwood and the timber is harvested for many commercial purposes such as to produce furniture, ship planking, poles, beams, vehicle bodies and railway sleepers (Gerry, 1952; MTC, n.d.).

According to Lim (1992) dammar has been one of the major forest resources harvested by the aborigines in Peninsular Malaysia for trading purposes since before the establishment of Melaka as an international port. Gerry (1952) reported that the resin obtained from Dipterocarpus spp. was also used as varnish, torches and caulk in Southeast Asia. In these modern days, dammar is still used by the aborigines, Malays and Chinese in Malaysia for spiritual and medicinal purposes, incense, and local trade. Hence, dammar from Dipterocarps and other resin producing plants are susceptible to unsustainable exploitation and illegal harvesting in Malaysia (Mohd-Rafi, 2020a & b). Adrian and Rizki (2019) in their case study of D. grandiflorus tapping in Indonesia, highlight the potential medicinal properties of Keruing oil or oleoresin, and suggested tapping of the tree as a sustainable alternative to felling for timber.

In addition, D. grandiflorus trees provide ecological services by reducing the occurrence of soil erosion in the forest (Orwa et al., 2009). The trees have also been planted to improve soil conditions as its high rate of litter deposition produces abundant decomposed organic matter that provides nutrients to the soil (CABI, n.d.).

Its global conservation status has been assessed as Endangered in the IUCN Red List (Ly et al., 2017). Populations of D. grandiflorus are decreasing world-wide due to habitat loss caused by land acquisition for agriculture and timber harvesting. However, in Malaysia, this species is listed as Near Threatened because although its habitat of tropical lowland forest is among the most threatened habitats globally, there are still many individuals in protected areas (Chua et al., 2010).