Clematis heracleifolia is a beautiful garden plant, and both the whole plant and its root are important in traditional Chinese medicine. Polyploids are usually more valuable because they exhibit increased biomass and content of effective compounds for medicinal plants. This research aimed to induce tetraploidy in C. heracleifolia by the apical meristem method using 0.2% colchicine. Apical buds were induced under three treatments (24, 48 and 72 h) to explore the best treatment time. Cytology identification was accomplished for the obtained mutants and diploid controls. It showed that the highest mutation rate of up to 80% was obtained with the 48 h treatment. The leaves of mutants were much broader, thicker, and showed lower leaf index compared with controls by morphology examination. There were significant differences between tetraploids and controls for stoma size and stoma frequency at the 0.01 or 0.05 levels. The chromosome number of most mutants was 32 (2n = 4x), while the chromosome number of diploid...