Biodiversity assessments carried out from 2008 to 2010 recorded 667 higher vascular plant species of 373 genera in 140 families in Ngoc Son-Ngo Luong Nature Reserve. Of these: 28 are threatened species listed in the Vietnam Red Data Book 2007, 7 are listed in Vietnam’s endangered species Decree 32/2006, 10 are in the International Union for Conservation Nature (IUCN) Red List 2008, and 14 are species endemic to Vietnam. Some populations of the rare Nghien (Excentrodendron tonkinense) can be found on limestone ranges inside the reserve in Tu Do and Ngoc Son communes. While many of the species here are found in other limestone formations elsewhere in Vietnam, in NSNL NR they are quite large and concentrated, even when compared to those found in neighbouring protected areas (Cuc Phuong National Park and Pu Luong Nature Reserve). Mun (Diospyros mun), a critically endangered species in IUCN’s Red List, is also located in the reserve. Trai (Garcinia fagraeoides), Cho Dai (Annamocarya sinensis), Dinh Vang (Fernandoa bracteata) and Lan Kiem (Cymbidium spp.) are other endangered trees species that are located within Ngoc Son Ngo Luong.
Evergreen forests on limestone are the largest subtype of forested areas in the reserve. Ngoc Son Ngo Luong’s forests provide many economically important plant resources, particularly in terms of their value to local communities. Yet, forests on limestone also hold the most significant biodiversity resources of the reserve and contain the highest variety of rare, endangered, and endemic plant species. The evergreen forest subtype is an important asset for biodiversity preservation and is a valuable resource for scientific research and ecotourism.
At present however this forest subtype is being degraded due to illegal exploitation. Two particularly high value tree species Garcinia fagraeoides and Excentrodendron tonkinense are being overexploited and have become increasingly rare in the reserve. To conserve biodiversity throughout the reserve, it is necessary to strictly protect the forests here in order to save one of the largest, richest, and last limestone ecosystems in northern Vietnam.
Further research carried out in 2011 in NSNL NR demonstrates the critical conservation value of the Mun (Diospyros mun), Nghien (Excentrodendron tonkinense), and Lan Kiem Dai (Cymbidium), Magnolia lilifera, Kmeria septentrionalis, Michelia gioi, and Michelia odorum; Begonia nimgmingensis and Begonia filiformis; and Theana vietnamica Aver., sp. nov These are the most significant species found in NSNL NR, since they have never been recorded in Cuc Phuong National Park and Pu Luong Nature Reserve. Therefore, a conservation action plan focused specifically on these taxa is urgently needed.