Flora includes evergreen cloud forest, sphagnum bog, and deciduous dipterocarp forest. The mountain has biological systems range from lowland dipterocarp forest to montane vegetations. Flora is primarily that of the Borneo lowland rain forest habitat, with dipterocarp trees predominating. The reserve is covered with lowland dipterocarp forest. The park features forest types including mixed deciduous, deciduous dipterocarp and dry evergreen. It favors dipterocarp, mangrove and riverine forests. In Thailand, it inhabits mixed deciduous, dry evergreen and dry dipterocarp forests. The region is covered in dry evergreen forest, mixed dipterocarp forest, and deciduous dipterocarp forests. They primarily inhabit peat swamp forest, tropical heath forest, and mixed dipterocarp forest. Grows near the coast behind mangrove forests and in mixed dipterocarp forests. Orangutans are mainly arboreal and inhabit tropical rainforest, particularly dipterocarp and secondary old growth forest. The majority of the forest is dipterocarp forests. Meanwhile, mixed dipterocarp forests is present up to 800 metres in altitude. Malaysia's rainforest's are made of a variety of types, mainly dipterocarp, swamps, and mangroves. The most common forest type found on Penang Hill is the hill dipterocarp forest.