Black walnut (Juglans nigra L.) is one of the most valuable North American forest species, and has been cultivated in Europe since 1629. It is now planted in many European countries, of which Hungary, France and Germany are the most representative. In Romania it has been cultivated since the end of the nineteenth century, especially in the western and north-western parts of the country, and now covers over 2100 ha. This paper focuses on the silviculture applied to the black walnut plantations in the Sacueni Forest District (north-west of Romania), a forest unit where mixtures with either North American (e.g. northern red oak, pin oak, bitternut hickory, black cherry, etc.) or European (e.g. pedunculate oak, Turkey oak, ash, Norway maple, small-leaved lime) forest species, covering hundreds of hectares, are frequently found. The biometrical performances of such plantations show the high potential of the species when used in favourable ecological conditions (e.g. lowlands, with mild climates, rich and deep soils, permeable and constantly supplied with water, etc.).