Botanical data from an ethnoarchaeological study of cereal and pulse crops in Greece are used to explore alternativesources of mixed crop samples. In addition to more or less pure “monocrops”, deliberately mixed “maslins” were grown to exploit the tendency of individual maslin components to perform more or less well under different growing conditions. Inevitably, therefore, the composition of these maslins was highly variable. Crop processing may introduce systematic bias into the composition of crop samples and is also deliberately used to manipulate the relative proportions of maslin components in a highly flexible manner. Both monocrops and maslins contain low-level contamination by other cultigens, and it is shown that these were mainly introduced with the seed corn and not through crop rotation or mixing on the threshing floor. Minor contaminants resembling the dominant cultigen(s) in growth habit, seed size, etc., are not only hard to remove but also tend to be tolerated. The implications of these observations are discussed for the interpretation of mixed archaeobotanical crop samples.