The ecoregion covers the area above 1800 m elevation on (from north to south) Tsaratanana (2,876 m), Marojejy (2,133 m), Ankaratra (2,643 m), and Andringitra Massif (2,658 m).

There are smaller areas of thicket in Anjanaharibe-Sud Special Reserve in the north and Andohahela National Park to the south.

The thickets are composed of evergreen woody shrubs and low trees, which form a single, often impenetrable stratum never more than 6 meters tall.

Native trees include Agauria salicifolia, Ilex mitis, Neocussonia bojeri, Razafimandimbisonia minor, Dodonaea madagascariensis, Tambourissa gracilis, Podocarpus rostratus, Vitex humbertii, Faurea forficuliflora, Pittosporum sp., and several species of Pterophylla.

[3] In much of the ecoregion, secondary grassland, established by regular livestock grazing and burning, has almost entirely replaced the original thicket vegetation.

The most common grasses on Ankaratra's secondary grasslands are Pentameris natalensis, P. humbertii, Andropogon trichozygus, Anthoxanthum madagascariense, Digitaria ankaratrensis, Agrostis elliotii, Merxmuellera macowanii, Brachypodium perrieri, Poa madecassa, P. ankaratrensis, and Festuca camusiana.