The rain forest covers almost 65% of the island of Siberut. This forest is a palace for the life of flora and fauna by providing a source of food and shelter as well as forest also serves as a supporter of the traditional life of the Mentawai people, especially as traditional medicine.
Botanical collection was first created by Ridley (1924) and produces a description of 33 new species. Some speceis plants have evolved unique characteristics to form an unusual morphology. For example Xanthophyllum villarii (Rubiaceae), an extraordinarily high in Siberut. This species is known only in the Philippines. Chloranthus officinalis (Chloranthaceae) grows very large when compared with each of these species in other areas. Phaeomeria minor (Zyngiberaceae) has the smallest size in the genus.
LIPI (1995) has managed to record about 846 species, 390 genera and 131 families of a group of trees, shrubs, herbs, liana and ephypit. Also identified 18 species of ferns and 5 species of mosses and fungi. The most important families are Euphorbiaceae (24 genera, 100 species), Orchidaceae (41 genera, 67 species), Rubiaceae (25 genera, 54 species) and Lauraceae (11 genera, 39 species). Dipterocarpaceae group which successfully accounted for as many as 20 species including 6 species of Dipterocarpus, 2 species of Hopea, 8 species and 4 species of Shorea Vatica.
An estimated 15% of plants in Siberut is an endemic species. Among others who have found is that as many as 6 species of endemic plants are: Mesua cathairinae (Clusiaceae), brevicalyx Diospyros (Ebenaceae), Aporusa quadrangularis (Euphorbiaceae), Baccaurea dulcis (Euphorbiaceae), subsymmetrica Drypetes (Euphorbiaceae) and Horsfieldia macrothyrsa (Myristicaceae).
As a result of the isolation of P. Siberut, other forms of endemic flora found in changing its form from the mainland of Sumatra such as sago is a staple food in the Mentawai which has more height and large that is the largest sago areas in Southeast Asia.
Rattan
Rattan is one of non-timber forest commodities are of significance for the economy in Siberut. In addition to producing cash, many types of rattan are very useful in daily life of society as a means to bind, wrap the leaves for a roof or traditional foods of sago (kapurut).
From the results of the inventory SNP (1999) found 15 species of rattan-rotanan in Siberut which consists of 3 genera are: Calamus 10 species, and Korthalsia Daemonorops 3 types of 2 types. From these types of wicker-rattan Calamus Calamus scipionum comfort and is a valuable economic, where rattan-cane is widely available in mixed primary forest.
Orchid
Wild orchids found in the area of SNP of 25 species included in 13 genera comprising 22 species of epiphytic orchids and 3 types of ground orchid (LIPI, 2002). Orchids are well known from Siberut is the White Moon (Phalaenopsis amabilis), white flowers thick fleshy leaves, long flowering 3-4 months with the number of florets 7-15 in one stalk. Other orchids that can be found is Coelogyne incrasata , Eria nutans, Dendrobium paphyllum etc.
