Simple SummaryThis paper is devoted to the study of theLunaria redivivapopulation at the eastern border of its range (National Park “Smolny”, Republic of Mordovia, Russia) in 2013–2018. Ontogenetic structure of the population has been identified by distinguishing juvenile, mature vegetative, and reproductive individuals. We found changes in the ontogenetic structure of the population from 2013 to 2018. The type of its population changed from vegetatively oriented to bimodal, with a decrease in proportion of mature vegetative individuals. We found a significant negative correlation between the fruit set and the moisture in mid-July, and wind strength in late May and early June. It was found that the number of both flowers and fruits per individual is significantly positively correlated with the precipitation in late April, and they are negatively correlated with these parameters and the temperature in late July. We assume that the habitat shading negatively influences theL. redivivapopulation status.AbstractLong-term studies of plant populations provide valuable knowledge on the influence of various environmental factors on plant species. The status of edge-range species populations is especially important to be studied due to their higher vulnerability to extinction. This paper aimed to study theLunaria redivivapopulation at the eastern border of its range (National Park “Smolny”, Republic of Mordovia, Russia). The study was carried out in 2013–2018. Assessment of theL. redivivapopulation was performed on the basis of individual parameters of plants (height of the individual, number of leaves per individual, number of inflorescences, flowers, fruits per one generative individual, and the fruit set), and density of individuals. Ontogenetic structure of the population was identified by distinguishing juvenile, mature vegetative, and reproductive individuals. The relationships between weather conditions (mean values of temperature, air moisture, wind strength, precipitation divided to three decades per month) and population parameters ofL. redivivawere identified. Results showed changes in the ontogenetic structure of the population. The type of its population changed from vegetatively oriented to bimodal, with a decrease (R2= 0.686) in the proportion of mature vegetative individuals. We demonstrated a significant decline in some parameters of theL. redivivareproduction. We found a significant negative correlation between the fruit set and the moisture at mid-July (r = −0.84,p< 0.05), and wind strength in late May (r = −0.83,p< 0.05) and early June (r = −0.83,p< 0.05). It was found that the number of both flowers and fruits per individual is significantly positively correlated with the precipitation in late April, and they negatively correlated with these parameters and the temperature in late July. We assume that the habitat shading negatively influences theL. redivivapopulation status.