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


Introduction
Due to the amateur efforts of Prof. T. Vilchynsky, northern white cedar, originating from the Atlantic coast of North America, was introduced in the mild humid climate of Lviv in the 1930s in one columnar and two pyramidal forms (Kharachko and Skolskyi, 2017).A number of pyramidal and columnar forms were introduced during this period.In the post-war period, A. Shcherbyna, an associate professor at the Ivan Franko State University of Lviv, discovered 5 ornamental forms in the landscaping of the city.In the seventies, a large number of cultivars of northern white cedar were introduced by R. Karmazin at the Ivan Franko State University.In the 1970s and 1980s, more than 10 ornamental forms were grown in urban nurseries.Kycheryavyi et al. (2021) found 43 ornamental forms, the vast majority of which are not used in urban landscaping.In our opinion, the main reason for this is the poor awareness among gardeners of the peculiarities of using a rich assortment to create garden and park compositions (Kycheryavyi et al., 2018;Kycheryavyi et al., 2021).T. occidentalis attracts the interest of many scientists in the fields of ecology, forestry, and medicine (Landsberg, 1981;Кlausnitzer, 1987;Czernecki and Jabłońska, 2016).In particular, the chemical components of T. occidentalis have been of interest for decades due to the essential oil, coumarins, flavonoids, tannins, and proanthocyanidins it contains.Pharmacology includes antioxidant, antiinflammatory, antibacterial, antifungal, antitumor, antiviral, gastrointestinal protective, radioprotective, antipyretic, and regulatory effects on lipid metabolism.T. occidentalis is widely used in landscape design.The features of the developmental stage, ornamental values, and varieties of garden hedges used as integral components of landscape architecture and urban design in Kosovo were investigated (Balaj, 2020).It was concluded that the studied varieties of Thuja sp. and Leylandii species should be included in the structure of the hedge planting for good urban landscape design.Another positive role of the plant was found in the absorption of dust particles from the air.The authors report the degree of absorption of dust particles from the air by some tree species.The presence of wax on the leaves was significant for the adhesion of particulate matter.All species captured dust, with their overall capture efficiency ranked from highest to lowest as follows: Thuja occidentalis > Hedera helix > Phyllostachys nigra.All types of green barriers contributed to the improvement of air quality by capturing dust particles, regardless of their location within the barrier (Redondo-Bermúdez et al., 2021).
The physiological features of growth are of considerable interest in different parts of the world.The study (Bouslimi et al., 2022) examined regional, local, inter-tree, and radial variations in ring density and width in Thuja occidentalis in the boreal forest of Quebec.The average ring density of trees growing at Abitibi-Témiscamingue was 356 kg m -3 , with slight variation between earlywood and latewood (167 kg m -3 ), revealing relatively homogeneous wood.Regional and local variations in growth and wood density parameters of T. occidentalis indicate a complex response to environmental factors.
This research reports the results of studies of six old growth stands of northern white cedar (Thuja occidentalis) in the Big Reed Reserve in northern Maine, USA, aimed at reconstructing the frequency and severity of past natural disturbances.Overall, 63% of cedar trees contained internal rot, and the likelihood of decay increased with the diameter.Evidence of growth thinning reveals irregular pulses of canopy disturbance with low to moderate severity (Fraver et al., 2020).A study by Johnson et al. (2022) compared seed biomass, morphology, seed set, and similarity between two natural populations and three additional seed sources of Thuja occidentalis L. in Chicago, Illinois.Differences between the two adjacent sites indicate that Trout Park (Site 1) is disproportionately affected by environmental factors (e.g., road salt and altered hydrology) compared to Chicago Elementary School (Site 2), potentially affecting the growth and reproduction of T. occidentalis in these urban populations.A large dataset of 842 T. occidentalis was randomly collected from favorable (cliff-top plateau) and unfavorable (cliff-side) habitats to determine whether trunk streaks were directly or indirectly related to age, growth rate, and habitat (Matthes et al., 2002).The earlywood tracheids of older trees had the most enormous pits, indicating that these trees are more sensitive to cavitationrelated scarcity of water than younger trees and supporting the hypothesis that tracheid cavitation is involved in trunk streak formation (Caruntu et al., 2020).Rooting percentage was significantly influenced by the cultivar and type of cuttings, while the root length was significantly influenced by the type of cuttings.A higher average percentage of rooted cuttings was recorded in the cultivar 'Smaragd' compared to the cultivar 'Columna' (Karlović et al., 2019).
Thuja occidentalis was introduced from North America.Northern white cedar, belonging to the Cupressacae family, is a well-known medicinal and ornamental plant.Thuja occidentalis, commonly known as American Arbor vitae or white cedar, is indigenous to eastern North America.It has medicinal properties.The plant was first recognized as a cure by native Indians in Canada during a 16 th -century voyage and was found to prove effective in the treatment of weakness from scurvy (Adhikary, 2020).In the countries of North America, the species is found in the wild.
Research on the development of other types of ornamental plants is conducted in the presented region.The peculiarities of under tree microclimate of Juniperus L. shrubs are presented.The studied plants were registered within the municipal area of the city of Lviv and its green belt.Temperature and humidity conditions of the under-tree space in summer and winter periods were studied in detail.A comparison of the indices of microclimate under the shrubs and the adjacent open area was carried out (Shuplat and Popovich, 2016).
Morphological features of shrubby stunted and stunted species and forms of junipers make it possible to form a sub-tent phytoclimate in the urbogenic conditions of the city of Lviv with increased air dryness and temperatures, providing favorable temperature and humidity regimes of air and soil for plants, contributing to the spatial development of bushes, increasing their vitality and decorativeness.The obtained microclimatic data on cloudy and sunny days are characterized by a greater difference in the values of air and soil temperature indicators than on cloudy days (Shuplat and Popovich, 2016).

Material and Methods
The aim was to identify the available cultivars of northern white cedar (Thuja occidentalis L.) available in the landscaping and ornamental nurseries of Lviv, determine their shape and color diversity, and evaluate their esthetics.
A route-visual method was used for identifying ornamental forms in landscaping and nurseries (Belochkina, 2006;Kycheryavyi and Kycheryavyi, 2019).The characteristic features of the plants were recorded: the shape and density of the crown, the nature of branching, the color of the needles, and the peculiarities of seed production.A scoring system based on existing methodological approaches was used to evaluate the decorative characteristics of the plants (Shlapak et al., 2014).
The research was conducted during 2015-2022 in the territory of the Lviv region in Ukraine. Figure 1 shows the layout of the studied objects.

Results and Discussion
The wide distribution of ornamental forms of northern white cedar in modern landscaping and nurseries in Lviv is a confirmation of its high esthetics.In general, the decorative qualities of plants are revealed during their development and depend on age, season, location in compositions, and landscaping elements.In this regard, we decided to determine the decorative qualities of its cultivars before designing landscape elements with ornamental forms of northern white cedar.A three-point scale for esthetic evaluation of plants was developed.It takes into account the most characteristic features: crown shape, needle color, branching pattern, seed production, and crown density (Table 1).Forty-three cultivars of northern white cedar were tested by this method (Table 2).The highest number of points ( 12) was given to 46.4% of the ornamental forms, 11 points to 16.3%, 10 points to 9.3%, and 8 points to 11.6%.Plants with a distinct regular crown shape, primarily columnar and spherical, received a high number of points.They can be widely used in hedges and container plantings, due to their good plasticity.In general, the vast majority (88.4%) of cultivars were characterized by a high decorative index.This indicator is related to the demand and professional selection made by the business.After all, the plant market is supplied with ornamental plants that meet the esthetic tastes of customers.

Design of elements and compositions
The existing compositional solutions of various landscaping elements using analyzed ornamental forms of northern white cedar indicate the lack of standard algorithms developed in forestation (schemes for mixing species).In any case, in modern landscaping, control over these decisions is given to gardening practitioners, who create rather primitive compositions at their own discretion.Because practitioners are unaware of the basic laws and principles of composition, and the richness of forms in dendroflora, they impoverish their psycho-emotional perception when creating plantings.The variants of application of gardening elements in garden and park compositions are suggested.

Solitary
Several possible variants of cultivars of northern white cedar were investigated as solitaries, including both trees and shrubs (Tables 3, 4).We took into account the wind resistance of the plants as well as their high esthetic and sanitary-hygienic properties.In parks, in open spaces, we recommend planting solitary trees with tall columnar ('Fastigiata', 'Columna', 'Spiralis') and pyramidal ('Pyramidalis', 'Douglasii Pyramidalis') shapes in the middle of the lawn or against the background of the forest edge opposite the viewpoint, with a distance of 3-4 m from it, where the tree is a transition from the massif to the lawn.We recommend introducing golden-yellow forms to contrast with the dark-leaved trees ('Aurea', 'Aureospicata ', 'Ellwagneriana Aurea', 'Wareana Lutescens').
We suggest planting the foreground solitaries separately in a place convenient for viewing.We recommend planting them in city squares and small gardens.Low (up to 5 m) columnar, conical, and pyramidal forms of trees and shrubs should be used for planting.The optimal distance from the viewpoint to the exposed solitaries should be two to five times the height of the tree.We also suggest using shrub forms as solitaries, for accentuating the foreground of a group, branching paths, or decorating an architectural construction.

Alley
Columnar and pyramidal forms, having a vertical impact on the open space, can be used to form compositional axes, accentuate the perimeter of the garden, and create a play of light and shadow.
Alleys with a simple rhythm, when the same shape is repeated at the same distance ('Fastigiata', 'Columna', 'Malonyana', etc.), are recommended for the entrance areas of parks, squares, and gardens (Table 5).
Table 5. Tree and shrub ornamental forms of northern white cedar in alleys with a simple and complex rhythm.

Green wall
Columnar, pyramidal and oval-ovoid shapes (height from 3.0 m to 3.5 m and higher) play a protective role (wind, dust, noise, snow), and also form a fence for various objects -gardens and squares, children's, sports, and household playgrounds, internal boundaries of gardens and allotments.Such walls can be used for visual isolation of unplastered walls and walls with unattractive views.
For green walls, we recommend columnar, pyramidal, and oval-ovoid shapes (Table 6).Walls using forms with golden yellow coloring are original.However, mixing green and golden-yellow colors should be avoided.The distance in the row for columnar forms is 0.5 m, for pyramidal -1.0 m.

Hedges
We recommend using borders, low and medium hedges to frame parterres, flower beds, front gardens, lawns, and paths.Low and medium-height trees and shrubs are suggested (Table 7).
We recommend planting the plants in trenches 50-60 cm deep in a single row (at a distance of 25-35 cm) or in several rows in a checkerboard pattern (spacing in the row 30-40 cm, between rows 20-35 cm).
The topiary work should be carried out at least 4 times during the summer on straight trapezoidal and semi-oval profiles.Despite the simplicity of the rectangular profile, we do not recommend it.Firstly, it forms rigid contours in landscape parks that are not characteristic of a free layout.Secondly, in such hedges, the down part receives less light, which leads to the death of small aerial branches and exposure of the trunks.

Bosquets
Medium-sized hedges in the form of a closed square, rectangle, circle, or other regular shape that delimit a place of rest or exercise, children's playgrounds and sports areas are called bosquets.We recommend upright tree and shrub forms with a dense crown for their creation.The height of the bosquet is 1-2 m.Tending of bosquets (topiary work) is the same as for ordinary hedges (at least 4 times during the summer).

Topiary
Topiaries are a variety of trimmed figures as a tribute to the distant past (this name, according to legend, comes from the name of the ancient Roman gardener Topiarius, a contemporary of Emperor Hadrian ) (Table 8).Topiaries are widespread in contemporary landscape gardening art.We have analyzed the modern trimmed decorative forms and proposed plants with good plastic qualities for topiaries.
For topiaries of various decorative and artistic forms, we recommend plants with dense crowns and thin branches pressed against the axial trunk.

Rocky gardens
Ornamental forms of northern white cedar are well represented in rocky gardens today, including spherical and pulvinate forms.

Conclusion
The high potential of ornamental forms of northern white cedar (88.4% of 43 identified in landscaping and nurseries) makes it possible to increase the estheticization level of green spaces.
Proposals for garden and park elements for decorative compositions (group, solitary, alley, green wall, hedge, bosquet, topiary, rockslide) allow the rational use of planting material, improve esthetics, and increase the durability of plants.
To increase the esthetic value of green spaces with ornamental forms of northern white cedar, it is recommended to use the developed models of compositional grouping based on symmetry, contrast, color, silhouette, crown size, and density.

Figure 1 .
Figure 1.The location scheme of the studied objects within the Lviv region.

ESTETSKA1
Department of Landscape Architecture, Park Gardening and Urban Ecology, National Forestry University of Ukraine, Lviv, Ukraine 2 Institute of Civil Protection, Lviv State University of Life Safety, Lviv, Ukraine R e z i m e

Table 1 .
The esthetic evaluation of northern white cedar cultivars (point scale).

Table 2 .
Summarized data on the esthetic evaluation of the ornamental forms of northern white cedar.

Table 3 .
Woody forms of northern white cedar as solitaries.

Table 4 .
Shrub forms of northern white cedar as solitaries.

Table 6 .
Woody forms of northern white cedar recommended for green walls.

Table 7 .
Forms of northern white cedar recommended for trimmed hedges.

Table 8 .
Forms of northern white cedar recommended for different types of topiaries.

Table 9 .
Ornamental forms of northern white cedar recommended for rocky gardens.