This study of changes in agrobiodiversity documents the domesticated species and, to a limited degree, the landraces, cultivated in the Siwa oasis of Egypt in 1919, 1924, 1968–1969, and 2004–2006. Siwa is ecogeographically and culturally isolated by more than 300 kilometers (km) from other agrarian communities and, perhaps because of this, detailed observations were made there by a number of agricultural scientists and geographers in a way that provides time-series data lacking from many other agrarian landscapes. Although I have drawn upon Siwan names for crops first published in 1890, this report may be the first substantive record of Tasiwit (Eastern Berber) folk names for traditional crops that allows ethno-linguistic comparisons with Cairene Arabic and other Northern Berber (Tamazight) dialects in North Africa. The perennial crop inventory of Siwan Berbers has remained relatively stable through time and few traditionally cultivated annual species or landraces have been lost. However, additional crop species from other parts of Egypt have been adopted since a paved road was completed to Siwa in 1986 and more Awlad Ali Bedouins have settled and begun dooryard gardens. The reasons for the relative stability of Siwan agrobiodiversity are discussed, and may relate to both the need for crop ecotypes adapted to the challenging alkaline conditions found in Siwan agroecosystems and Siwan pride in and adherence to its traditional cuisine.