In order to elucidate the extraction kinetics of valuable organic substances from dried vegetable materials, extraction of pyrethrins from ground pyrethrum blossoms was taken as an example and studied at various conditions. It was shown that the apparent diffusivity is a nonmonotonous function of the solute content in the solid phase. Due to the superposition of several phenomena, its value passes through a maximum and may change a hundred or even more times. Simple laboratory batch experiments and numerical solution of the appropriate extraction models are necessary prerequisites for successful design of large-scale extraction processes of vegetable raw materials.