Shifting cultivation is a type of farming without fixed boundaries. It obeys an ecological logic but requires constant improvisation and adaptation to fluid circumstances. The character of improvisation in shifting cultivation is explored with reference to an African case study (rice farming by the Mende people of Sierra Leone). Two elements are emphasized in particular—the management of fire (by men) and rice seeds (by women). A contrast, applicable not only to farming, but also to other activities such as military conflict and musical performance, is drawn between strategic planning and tactical improvisation. The relevance of Mary Douglas’s grid-group theory to the framing of the social skill sets required for improvisation is discussed.