Contrary to popular opinion the forest floor is usually too dark to support much ground cover. About half the trees belong to the Dipterocarp family, which supplies Sabah State's timber production. Notwithstanding this, diversity is the keynote of the tropical forest and some thousands of species can be found. An unusual component of the flora is the parasitic Rafflesia plants, which produces a fleshy red flower up to 45 cms in diameter. Between 912 metres and 1,824 metres elevation is the montane forest, occupying almost half of the Park's area.
Trees are smaller and ground cover is much denser because more light reaches the ground.
Increased moisture from low clouds leads to an abundance of epiphytes, such as orchids and mosses grows on the trunks and branches of trees. Species composition is almost wholly different from the lowland forest, oaks, chestnuts, laurels, myrtels, etc are abundant. Park Headquarters is located within this zone. Most fascinating to visitors is the mossy or cloud forest that extend upwards from 1,824 metres. Here gnarled, often stunted trees are covered thickly with mosses, lichen and orchids.