Crops that were initially introduced as foreign vegetables, such as corn, sweet potato, and potato, have diverse word forms in Sinitic languages. This paper, based on large-scale data, investigates the spatio-temporal distribution of the modifying morphemes in the compound nouns of such crops, including 胡 hú ‘foreign’, 番 fān ‘foreign’, 洋 yáng ‘oceanic, foreign’, 西 xī ‘Western’, 海 hǎi ‘oceanic’, 荷兰 Hélán ‘Holland’, and 倭 Wō ‘Japan’. These morphemes share one prominent geographical pattern: they take as a core the region where the crop was first introduced. While some show multidirectional distribution, e.g., the 番 fān ‘foreign’ category, some show unidirectional distribution, e.g., the 洋 yáng ‘oceanic, foreign’ category. Diachronically, 胡 hú ‘foreign’ and 番 fān ‘foreign’ precede 洋 yáng ‘oceanic, foreign’ and 西 xī ‘Western’. Such spatio-temporal distribution can be accounted for by semantic change, sociocultural development, geomorphological environment, and the history of intercultural communication.