Indo-China

Indo-China stretches across mainland Southeast Asia, taking in Myanmar, Thailand, Laos, Cambodia, and Vietnam. The Mekong River anchors the region, flowing through five countries on its way to a vast delta on the South China Sea, while the Irrawaddy, Salween, Chao Phraya, and Red rivers drain the parallel mountain chains that frame the peninsula. The climate is tropical and monsoon-driven — a long wet season followed by a marked dry season — but altitude shifts the picture quickly. Lowland rainforest, dry deciduous forest, limestone karst, mangrove delta, and cool montane cloud forest can all occur within a few hours' drive of each other.

Elevation runs from sea level to 5,881 metres at Hkakabo Razi in northern Myanmar, the highest peak in Southeast Asia. South of there, the Annamite Range (Truong Son) and Cardamom Mountains form long, isolated montane refugia where Vietnamese, Lao, and Cambodian endemics have evolved in pockets — and where saola, Annamite striped rabbit, and an unusually high count of locally restricted plant species still survive. The central Myanmar dry zone and Thailand's central plain support mixed deciduous forest dominated by teak (Tectona grandis) and Dipterocarpaceae, while the Mekong floodplain and Tonlé Sap basin add seasonally flooded forest and freshwater swamp.

The flora is exceptional even by tropical standards. Dipterocarp giants — Dipterocarpus, Shorea, Hopea — dominate the canopy. Below them, Orchidaceae reaches some of its global diversity peaks: slipper orchids (Paphiopedilum), Dendrobium, Coelogyne, Aerides, and Bulbophyllum species, many of them endemic to single limestone outcrops. Gesneriaceae (Aeschynanthus, Henckelia, Petrocosmea) and Begoniaceae micro-radiate across the same karst, while Araceae (Alocasia, Homalomena, Aglaonema, Schismatoglottis) and Zingiberaceae gingers carpet the forest floor. Many familiar terrarium plants come straight from this region — Pilea cadierei (the Vietnamese aluminium plant), Ludisia discolor (jewel orchid), Aeschynanthus radicans (lipstick plant), Microsorum musifolium, Bolbitis heteroclita, and several Pyrrosia ferns are all native here.

Indo-China sits at the centre of the Indo-Burma biodiversity hotspot. The orchid and aroid catalogues of the late twentieth century lean heavily on collections from northern Vietnam, the Cardamoms, and the Shan plateau of Myanmar.