Hopea hainanensis, a tree species in the genus Hopea (Dipterocarpaceae), is an indicator plant of Hainan rainforest.

Protection class

It is a Class I national key protected wild plant. It is also listed as Endangered (EN) on the IUCN Red List of Threatened Species and the China Plant Red Data Book.

Distribution and habitat

Hopea hainanensis is distributed in Hainan (Sanya, Ledong, Changjiang, Baisha, Wuzhishan, Wanning, Lingshui, Qiongzhong, Baoting, Qionghai, Dongfang and other mountainous areas), Guangdong (Hepu), Yunnan, Guangxi (Nanning, Qinzhou), Fujian (Fuzhou), and other provinces in China. It is also introduced to tropical areas of South Asia.

The plant grows in dense forests at elevations around 700 meters. It can adapt to hot, moist and damp habitat in calm wind, and it is often mixed with Manglietia hainanensis Dandy, Homalium hainanense Gagnep., Ficus auriculata Lour., and Schefflera octophylla (Lour.) Harms.

Morphological characteristics

Hopea hainanensis is an evergreen tree that can grow 10-20 meters tall. Its leaves are leathery, elliptical or oblong-elliptic, about 7-12 cm long and 4-6.5 cm wide. The leaves are short and acuminate at the apex, and slightly rounded on the base. Dry leaves are yellowish brown on both sides, covered with tiny powdery scales. There are 7-9 sets of lateral veins on a leaf, with protrusions on the lower part and parallel thin veins that are not obviously visible. The petiole is 1.5-2 cm long and rugose. Its flowers are arranged in acrogenous panicle inflorescences (3.5-7 cm) and in the upper axil of leaves, with star-shaped small pubescence. The small flowers are mainly distributed on the side of the branch of inflorescences and densely covered with gray pubescence. The peduncle is thick. The flower of the plant is very short. The calyx-lobe is leathery in the elliptical oval shape and with a length of about 2.5 mm. It is sunken and rounded at the top, densely covered with gray pubescence outside. 15 stamens are arranged into two rounds before the mature flowers are observed, with wide and thin filaments on the lower part outside (abruptly narrowed at the top), and linear filaments inside. All the stamens have no pubescence. The anthers are oval and elliptic, and the filamentous appendage on the top of the connective is about 1 mm long. The near-cylindrical ovary has no pubescence and the style is short. The fruit of the plant is oval, about 1.5 cm long, with short and convex tip at the top. There are adhesives on the fruit surrounded by enlarged persistent calyx. Two oblanceolate calyx lobes expand into the shape of wings, and they are about 7 cm long, with 9-11 longitudinal veins. Flowering lasts from June to July, and the fruits are available in November and December.