Most of the vegetation within Hoollongapar Gibbon Sanctuary is evergreen in character and is composed of several canopy layers.

The upper canopy consists mostly of Dipterocarpus macrocarpus rising 12 to 30 m (39 to 98 ft) and having straight trunks.
 Other species found in the top canopy include Sam (Artocarps chaplasha), Amari (Amoora wallichi), Sopas (Mcheliai spp.),
Bhelu (Tetramels mudiflora), Udal (Sterculia villosa) and Hingori (Castanopsis spp.).

Nahar (Mesua ferrea) dominates the middle canopy with its spreading crown, casting fairly heavy shade over a wide area.
 Other species that make up the middle canopy include Bandordima (Dysoxylum procerum), Dhuna (Conarium resiniferum), Bhomora (Terminalia belerica), Ful Gomari (Gmelina sp.)
Bonbogri (Pterospermum lanceafolium), Morhal (Vatica lanceafolia), Selleng (Sapium baccatum), Sassi (Aqualari agolacha), and Otenga (Dillenia indica).

A variety of evergreen shrubs and herbs make up the lower canopy and ground layers.
 The most common of these are Dolu bamboo (Teinosstachyum dullooa), Bojal bamboo (Pseudostachyum polymorphum), Jengu (Calamus erectus), Jati bet (Calamus spp.),
Houka bet (Calamus spp.),
Tora (Alpinia allughas), Kaupat (Phrynium imbricatum), and Sorat (Laported cremulata).
Most of the vegetation within Hoollongapar Gibbon Sanctuary is evergreen in character and is composed of several canopy layers.
The upper canopy consists mostly of Dipterocarpus macrocarpus rising 12 to 30 m (39 to 98 ft) and having straight trunks.  Other species found in the top canopy include Sam (Artocarps chaplasha), Amari (Amoora wallichi), Sopas (Mcheliai spp.), Bhelu (Tetramels mudiflora), Udal (Sterculia villosa) and Hingori (Castanopsis spp.).
Nahar (Mesua ferrea) dominates the middle canopy with its spreading crown, casting fairly heavy shade over a wide area.  Other species that make up the middle canopy include Bandordima (Dysoxylum procerum), Dhuna (Conarium resiniferum), Bhomora (Terminalia belerica), Ful Gomari (Gmelina sp.) Bonbogri (Pterospermum lanceafolium), Morhal (Vatica lanceafolia), Selleng (Sapium baccatum), Sassi (Aqualari agolacha), and Otenga (Dillenia indica).
A variety of evergreen shrubs and herbs make up the lower canopy and ground layers.  The most common of these are Dolu bamboo (Teinosstachyum dullooa), Bojal bamboo (Pseudostachyum polymorphum), Jengu (Calamus erectus), Jati bet (Calamus spp.), Houka bet (Calamus spp.), Tora (Alpinia allughas), Kaupat (Phrynium imbricatum), and Sorat (Laported cremulata).
Hoollongapar Gibbon Sanctuary