The anti-gibberellin ancymidol was tested on three daylily hybrid clones to evaluate its ability to foster internode shortening of in vitro cultured shoots. At concentrations as low as 0.04 µM shoot height was reduced to ~ 50% of controls after six weeks exposure. Leaves of 'dwarfed' shoots or plantlets were 2 to 10 times shorter than control leaves and were more typical of leaves produced by mature, rather than juvenile plants. "Ancymidol leaves" showed overlapping bases and the "keel" or central dorsal ridge on the abaxial side of the leaves became more prominent and assumed a fan-like appearance. Because the leaves were more concave on the adaxial surface, they presented a "cupped" or canaliculate, longitudinally grooved morphology. Roots produced by ancymidol-grown plants were thicker and more fibrous than control roots, again a feature of mature phenotype. Shoots grown for protracted periods (ca. 14 to 16 weeks) showed a substantial increase in shoot production. At concentrations below 0.39 µM there was no effect on multiplication but as the ancymidol concentration increased, multiplication increased. There were differences in responsiveness to ancymidol among the clones for bud multiplication. Effects of ancymidol on phenotype and multiplication were reversible.