Aim: Orchids make up 8% of Madagascar's vascular plant species richness and are typically associated with the island's forests. Yet most of the island is covered by open ecosystems, long dismissed as degraded. This perception has contributed to their neglect, limiting our understanding of species ecology and hindering conservation action in this global biodiversity hotspot. Using orchids, we provide a novel understanding of plant diversity patterns across Madagascar's ecosystems. Location: Madagascar. Methods: We assessed the ecosystem attribution of the 884 orchid species of Madagascar among closed (forest) and open (grassy, marsh, rocky outcrop, scrub) ecosystems. We analysed the taxonomic composition, richness, environmental niche, geographic patterns, phenology, and collection patterns of orchids using a mix of herbarium, publication, and iNaturalist data. Results: We find that 31% of Madagascar's orchid species occur in open ecosystems, with 17% restricted to them. These species match closed-ecosystem species in degree of endemism to Madagascar (~85%) but are associated with higher elevations, fire, and pronounced precipitation seasonality, and are distributed particularly in the grassy Central Highlands, a region historically undervalued ecologically compared to humid forests. Temporally, open-ecosystem specialist orchids exhibit strongly synchronous, brief wet-season flowering, unlike the more diffuse flowering observed throughout the year in forests. Conclusions: We reveal a distinct component of Madagascar's orchid flora, demonstrating that open-ecosystem species represent high endemism and ecological specialisation, with implications for understanding biogeography and conservation planning across tropical landscapes. These results provide an evidence base for open ecosystem conservation and suggest that other taxa may also be under-represented in our understanding of Madagascar's open-ecosystem biodiversity. Re-evaluating open ecosystems can uncover overlooked dimensions of species diversity and ecological function, informing more balanced conservation strategies across contrasting ecosystems.