This project focuses on sown grasslands in Britain, New South Wales, and Cape Colony in the age of "Enlightened" agricultural science (1750-1860). I observe two parallel processes at play in this time period: 1) Britain's "New Husbandry," a form of intensive agricultural cultivation based primarily on grass-based crop rotation and increased livestock production (mixed husbandry), and 2) the settler revolution in what would become the British Commonwealth following the loss of the American colonies. I suggest that these seemingly discrete developments are, in fact, related, and that this becomes evident when we uncover the part grasslands have played in agrarian development throughout the Empire. I examine the role of grassland cultivation in colonial responses to ecological thresholds, namely soil fertility. I question both the portrayal of ecological imperialism as a largely unsupervised phenomenon and the interpretation of settler practices as singularly exploitative. I do this by examining the scientific networks overseeing biological transfers and the "on the ground" efforts of settlers to establish agrarian sustainability. My overarching argument is that grasses became the calculated foot-soldiers of agrarian development in the settler empire and were, therefore, foundational in the history of British settler colonialism and fundamental to understanding environmental transformations in these territories.