There were 12 only terrestrial orchids found at Khao Nan National Park nature trails. Terrestrial orchids grow on moist areas such as forest floor and moist rocks. Among these terrestrial orchids, nine saprophytic orchids were found. Saprophytic orchids have on chlorophyll and grow on dead or decay organic matter. They must rely on fungi that attach their roots to provide nutrient. Because of the rather high species diversity, Khao Nan National Park is thus an interesting area for studying terrestrial orchids and mycorrhizal fungi that associate with their roots.