The article presents the biomorphological features of Helleborus foetidus L. at different stages of ontogenesis. The latent, virginal, and partially generative periods of development under the conditions of introduction of the species in the National Dendrological Park «Sofiyivka» of the National Academy of Sciences of Ukraine were studied. Indicator signs of age-related states, their duration and main characteristics were established. It was found out that the fruits ripen in the middle of June. Seeds (sm) are brown in color, bean-shaped, 4.8±0.5 mm long, 2.1±0.3 mm wide, weight of 1000 seeds is 13.4±0.3 g. Indicator signs of the onset of juvenile age (j) are the appearance of true leaves and the formation of lateral roots. The duration of this agerelated state is about three months. An indicator of the transition of individuals of H. foetidus to the immature age state (im) is the beginning of shoots branching. Signs of basitonia characteristic of H. foetidus appear at the initial stages of ontogenesis. In the virgin age (v), the branching of the shoots increases to the third order, additional roots are formed in the places where the basal areas of the lateral shoots touch the surface of the substrate. In the generative period, a hidden generative age state (g0 ) is distinguished, the indicator signs of which are the appearance of a transitional type of leaves (with short, wide petioles and a blade much smaller in size than typical leaves of the middle formation) and a characteristic thickening at the shoot top with embryonic inflorescence inside. The total duration of the virginal period of the ontogenesis of H. foetidus in the introduction conditions is about 18 months. The generative period is longer than the virginal period.

Key words: Helleborus foetidus, age states, seedlings, virginal period, generative.