Abstract Clematis crassifolia and Clematis cadmia Buch.-Ham. ex Hook.f. & Thomson are herbaceous vine plants native to China. C. crassifolia is distributed in shaded areas, while C. cadmia mostly grows in bright, sunny conditions in mountainous and hilly landscapes. To understand the potential mechanisms involved in the irradiance responses of C. crassifolia and C. cadmia, we conducted a pot experiment under three irradiance treatments with natural irradiation and two different levels of shading.