Australian bipinnate acacias, known locally as mimosa, are widespread on the plateaus and mountains of Madagascar. Rarely, however, do these trees attain their full size, leading to a surprising landscape of ‘scrubby’ wattles. We review the introduction of the wattles, survey their multiple uses in rural livelihoods and environmental management, and analyze the forestry policies, tenure rules, and ecological factors that maintain the trees' scrubby state. This well-adapted plant is an important resource for farmers and serves to green treeless hills, but it may become a conundrum to conservation managers due to its non-native, invasive status.