Esthetic assessment of the ornamental forms of northern white cedar (Thuja occidentalis L.) and their use in garden and park compositions

Northern white cedar (Thuja occidentalis L.) is represented in the world by about 200 ornamental forms, 43 of which were discovered and described in landscaping and nurseries of Lviv. The first plantations in Lviv date back to the 1920s. They were introduced by the professor at the Medical Institute T. Vilchynskyi, who brought material for cuttings from a nursery in Kurnik (Poland). The decorative qualities of these cultivars were determined on the basis of characteristic features and evaluated in points: the shape and density of the crown, the color of the needles, the nature of branching, and the features of seed-bearing. These decorative qualities formed the basis for the construction of various elements of garden and park compositions with the participation of tapeworms, alleys, green walls, hedges, boskets, topiaries, and rock gardens. The highest number of points (12) was obtained by 46.4% of ornamental forms, 11 - 16.3%, 10 - 9.3%, and 8 -11.6%. Cultivars with a distinct regular crown shape received high evaluation points. The options for the spatial arrangement of individuals were proposed and the distance between seating positions was recommended. Taking into account the high plasticity of cultivars and the ability to form crowns, variants of clipped hedges and topiaries were recommended. Several models have been proposed based on the distribution of ornamental plant groups based on their symmetry, silhouettes, alignments, contrasts, colors, density, and sizes. Cultivars were selected for each variant, and their group arrangement was proposed.