The range of occurrence of English oak (Quercus robur L.) occupies almost all of Western and most of Eastern Europe (except for northern regions), extending to the east to the Ural Mountains [1]. Resumption of oak under the forest canopy, in other words, the ability to generate self-seeding and trustworthy undergrowth, allowing to provide a generational change, deteriorating in the direction from the western regions to the eastern area; the intensity of renewal can vary dramatically in different species composition and completeness of the forest types in the same area [2, 6]. Quercus robur L. is indigenous, and one of the main forest-forming species in Ukraine, which has a high adaptive capacity, which contributes to long-range transport of pollen to 50-80 km [5]. Oak generates high-quality sustainable plantations in the steppe zone, but according to the literature and the experience of steppe afforestation has no perspective on natural regeneration by seeds in artificial plantations and ravine forests [3]. Populations of Quercus robur L. in the steppe zone are of interest for the study of general biological positions, as they are formed during the long evolution in dry conditions (annual rainfall of 350-450 mm), and now extreme effects of climatic factors increasing due to global change climate, this contributes to high arable agricultural land (90%), as well as the presence of environmental contaminants [4]. The purpose of this study was to investigate the phenotypic variability, population differentiation resumption of English oak in the steppe zone of Ukraine on the example of the Donbass region. Morphological characteristics of leaves, which are characterized by high genotypic conditionality and are often used in population studies, were used as phenotypic traits to assess variability and population structure of the resumption of oak. We analyzed 11 morphological characters (including 3 relative characteristics) in three hierarchical levels of sampling within each tree (endogenous variability) within each trial population (individual or intrapopulation volatility) and between populations (ecological-geographic or interpopulation variability). In total, 12 populations of Quercus robur L., growing in the Donbass, in villages Yarovaya, Bokovoe, Novodonetskoe, Elizavetovka, Nikolskoe, Olginka, Maloyanisol, Starodubovka, reserves – Zaplava-1, Azov dacha, Velikoanadolskiy forest and the Regional Landscape Park - "Kleban-byk", were analyzed. Maximum length of the leaves is fixed in populations of the forest reserve Zaplava-1 – 137.59 mm and the smallest – in the village Novodonetskoe – 116.56 mm. The maximum length of petioles revealed in populations of the forest reserve Zaplava-1 - 7,41mm, the minimum in the village Olginka – 5.47 mm. The widest leaf blades were marked in the forest Velikoanadolskiy and the village Yarovaya – 87.56 mm and 87.61 mm respectively, the narrowest – in the population situated in the village Bokovoe – 63.62 mm. Maximum width of the leaf was found in the population of the reserve "Azov Dacha" – 52.15 mm, the smallest – in the village Novodonetskoe – 33.43 mm. The number of blades of the highest value is characteristic of the population, situated in the village Elizavetovka – 11.03 pcs., The smallest populations "Azov Dacha" and Bokovoe – 9.67 pc. and 9.71 pc. respectively. Maximum angle of veining in the population of the village was recorded in Starodubovka – 46,27 °, the smallest – in the population Novodonetskoe – 43,3 °. The highest dissected leaf stands – Starodubovka village population – 0.527, the lowest – reserve Zaplava 1 – 0.357.  The results of field studies have allowed a clear distinction between the populations of oak and informatively describe the morphological characteristics of this type of plant. The following characteristics are the most variable: the length of petiole, the width of leaf blades, the width of the leaves and the length of the line from the bottom to the widest place of the leaf. Preservation of the gene pool of species in the region shall be adapted to the type of population differentiation and the choice of the populations with the highest level of phenotypic variability, such as Yarovaya, Zaplava-1 and Velikoanadolskiy forest.