The present invention addresses the problem of providing a method for producing plants in order to obtain a plant having a high content of caffeoylquinic acid compounds. The present invention also addresses the problem of providing a method for producing processed plant products. The method for producing plants according to the present invention has a step for growing at least one plant selected from the group consisting of potatoes other than sweet potatoes, plants from Convolvulaceae and plants from Asteraceae; and a step for subjecting the grown plant to hydroponic cultivation using a nutrient solution that substantially does not contain nitrate ion and substantially does not contain phosphate ion.