Application of growth stimulators can be especially effective on plantlets in vitro of tree species which are usually worse rooted and adapted in comparison with annual plants. In our work we evaluate effects of natural (dihydroquercetin, Zircon) and synthetic growth stimulators (Melafen, Fumar, Epin-Extra) on rooting and acclimatization of common ash (Fraxinus excelsior L.) microplants. The 0.05% - 0.2% Zircon and 10^-5% Melafen enhanced in vitro rooting by 29% - 37% and 31%, respectively. Melafen also stimulated root formation faster compared to control plants. The dihydroquercetin concentration of 0.01% increased rooting by 24% and root number per shoot by 1.8 times. In vitro plants rooted on media supplemented with Melafen, Fumar and Zircon demonstrated enhanced ability to adapt to non-sterile conditions and accelerated growth. Two months after planting to the greenhouse, plants rooted on 0.01% dihydroquercetin were 45% taller than the control. Weekly spraying of plantlets with 0.02% Epin-Extra containing 24-epibrassinolid stimulated growth of uniform plants with large leaves. The obtained results support the use of growth stimulators for application in clonal micropropagation of common ash both for large-scale production of planting stock and for conservation of rare and valuable genotypes.