Effects of Soil–Sand Mixtures on Alchemilla mollis and Geranium psilostemon: A Multi-Criteria Performance Analysis Under Low-Altitude Conditions Using PROMETHEE

Abstract

The selection of suitable growing media plays a vital role in the successful adaptation of high-altitude plant species to lowland urban landscapes. This study assessed the morphological and physiological performance of two native perennial species, Alchemilla mollis and Geranium psilostemon, under low-altitude conditions using three different soil–sand (mil) mixtures: TA (50% soil–50% sand), TB (75% soil–25% sand), and TC (100% soil). Over a 17-month period, key plant growth parameters—including height, canopy diameter, leaf number, and chlorophyll concentration—were systematically monitored. Additionally, soil samples were analyzed before and after cultivation to determine pH, total nitrogen, organic matter, organic carbon, phosphorus, and electrical conductivity levels. To evaluate overall performance, the PROMETHEE multi-criteria decision-making (MCDM) method was applied, incorporating 11 criteria spanning plant development, soil quality, and economic considerations. Results revealed that the TC medium offered the most favorable outcomes for both species, particularly in terms of chlorophyll content and biomass accumulation. Conversely, the TB medium supported higher retention of nitrogen and organic matter. While A. mollis exhibited greater resilience under suboptimal conditions, G. psilostemon demonstrated rapid development under favorable settings. These findings underscore the potential of native perennial species in sustainable landscape design and validate the use of MCDM approaches in optimizing plant–soil interactions in horticultural applications.

1. Introduction

High-altitude plants have developed various adaptation mechanisms in response to harsh environmental conditions such as low temperatures and ultraviolet radiation in their native ecosystems [1,2,3]. The ecological adaptation of these plants is shaped by the interplay between climate, soil structure, and biodiversity. In particular, tolerance to low temperatures, intense UV radiation, oxygen deficiency, and water stress plays a critical role in the survival of plants growing in alpine regions [4,5,6].

Plants thriving under such conditions have developed energy-conserving strategies by slowing down their metabolic activities in order to adapt to short growing seasons and cold temperatures [7,8]. Accompanied by these physiological adjustments are evolutionary adaptations that increase their stress tolerance and optimize senescence and flowering cycles in accordance with climatic constraints [9,10,11]. For instance, plants adapted to these environments often develop deep and extensive root systems, enabling more efficient access to water and nutrients [12,13]. Moreover, their ability to synthesize protective metabolites against high UV exposure enhances their capacity to cope with environmental stressors [14,15,16].

Ensuring ecological integrity in landscape design, planning, and implementation processes requires the deliberate use of native plant taxa as vegetative materials [17,18]. High-altitude plant species are notable not only for their resilience to environmental stressors but also for their functional roles within their native ecosystems. These plants provide a range of ecological services, including erosion control, regulation of the water cycle, and the conservation of local biodiversity [10,13,19]. Moreover, their demonstrated resistance to changing climatic conditions makes them highly valuable in sustainable landscape planning [4,5].

However, despite their ecological significance, there remains a notable gap in understanding how alpine plants respond to low-altitude urban conditions over extended cultivation periods. Few studies have quantified their physiological and morphological adaptation when transplanted into warmer, more variable city environments.

Alchemilla mollis, a perennial species belonging to the Rosaceae family, is native to the mountainous and humid regions of Central and Northern Europe and is also naturally distributed across northern and western parts of Turkey. It typically grows to a height of 20–60 cm and is characterized by heart-shaped leaves and yellow-green flowers [20,21,22]. This species thrives in soils with high water-holding capacity and is frequently used in landscape architecture due to its effectiveness in erosion control, visual cohesion, and ground cover functionality. In addition to its landscape value, A. mollis has long been recognized in traditional medicine for its antimicrobial and antioxidant properties [23,24]. Turkey plays an important role in the natural distribution of this species, contributing to both the ecological and cultural dimensions of plant biodiversity [21].

In practical applications, A. mollis is commonly utilized in perennial borders, rock gardens, and semi-shaded urban parks due to its low maintenance and ornamental foliage.

Geranium psilostemon is a perennial herbaceous species belonging to the Geraniaceae family, typically found at altitudes ranging from 1400 to 2400 m. It is naturally distributed across parts of the Caucasus and Central Asia. Flowering occurs between June and September, during which the plant displays vibrant blooms and distinctive foliage, making it highly valuable from an ornamental perspective [22]. Ecologically, it contributes to the continuity of genetic diversity by facilitating interactions with pollinators. Furthermore, its secondary metabolites hold medicinal potential, making the species significant for both traditional and modern phytotherapy applications [25,26,27].

In urban green spaces, G. psilostemon has been increasingly favored for its adaptability to diverse soil types and its strong visual impact, particularly in informal plantings and pollinator-supportive gardens. In landscape practices, its ability to adapt to diverse soil conditions enhances its usability in urban settings by offering both aesthetic and functional contributions [22,28].

Today, the functional and sustainable roles of plants are increasingly emphasized in landscape design, beyond their ornamental qualities. With the growing interest in plant diversity, there is a reinforced call for incorporating more native taxa into landscape compositions [29,30,31]. In this context, the ecological and cultural significance of native and locally adapted plant species continues to gain importance in the formation of sustainable landscapes.

Understanding the environmental requirements and growth behaviors of such species is essential for integrating them into climate-resilient, resource-efficient planting schemes.

In studies investigating the adaptability of such species to new altitudinal or environmental conditions, the properties of the growing medium to which they are introduced play a vital role. Soil serves as a decisive factor for plant development due to its physical, chemical, and biological characteristics. The structure of the root zone directly affects nutrient and water uptake, as well as the development of root systems [32,33]. In particular, attributes such as water-holding capacity, aeration, and nutrient content are critical in determining root performance and, consequently, the overall growth potential of the plant [34].

The physical and chemical components of the growing medium directly influence physiological processes such as root morphology, water uptake, and nutrient absorption in plant materials used in landscape applications [35,36]. For the establishment of a sustainable perennial garden, proper mixing ratios of components such as soil and sand (mil) are essential to ensuring optimal root development through enhanced water retention capacity and air permeability [37,38,39]. From this perspective, the composition of the subsoil is a critical determinant, particularly in the successful cultivation of long-lived herbaceous plants.

Chlorophyll content is not only an indicator of photosynthetic capacity but also a physiological marker of plant resistance to environmental stress. Soil type, water availability, and the characteristics of the growing medium can lead to significant variations in this biochemical parameter [40,41,42]. Therefore, assessing the effects of different growing media on chlorophyll synthesis offers valuable insights into plant productivity and overall ecosystem health [43,44]. A quantitative evaluation supported by detailed data is crucial when studying such adaptation-oriented species.

Multi-criteria decision-making (MCDM) methods offer a structured approach to simplifying complex evaluation processes where multiple factors must be considered. Among these, PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations) stands out due to its user-friendly structure and advanced statistical capabilities, enabling its application across a wide range of disciplines [45].

Several studies have demonstrated the applicability of the PROMETHEE method across biological and environmental domains. Some have focused on determining optimal anesthetic concentrations in aquaculture by evaluating physiological and histological responses of fish to herbal mixtures [46], while others have applied a fuzzy-based PROMETHEE model to rank SARS-CoV-2 IgM antibody tests using diagnostic performance criteria such as sensitivity, specificity, and predictive values [47]. These examples highlight the method’s flexibility and value in supporting complex decision-making processes. Building on these diverse applications, the method also offers significant advantages in horticultural and landscape planning contexts. Particularly in horticulture and landscape design, PROMETHEE allows practitioners to integrate ecological, agronomic, and economic variables into a single decision framework.

The PROMETHEE method is distinguished by its flexibility and visual interpretability, particularly in contexts where multiple criteria must be compared. It enables decision-makers to evaluate alternatives based on both quantitative and qualitative data [46,47]. Especially in fields such as plant production, agricultural applications, and landscape assessment—where numerous indicators must be considered simultaneously—PROMETHEE offers a rational, systematic, and graphically supported decision-making approach [48,49].

Therefore, the objective of this study is to assess the morphological and physiological responses of Alchemilla mollis and Geranium psilostemon under lowland conditions using three different soil–sand growing media. A multi-criteria decision-making approach (PROMETHEE) was adopted to integrate plant growth, soil quality, and cost-effectiveness into a comprehensive evaluation of substrate performance.

2. Material and Method

2.1. Plant Material

In this study, the plant excavation procedures were conducted in the Değirmendere Basin, located in the Black Sea region of Türkiye, specifically within Trabzon Province. The plant materials used were Alchemilla mollis (Rosaceae family) and Geranium psilostemon (Geraniaceae family). These species, which naturally grow in high-altitude regions, were transferred to a low-altitude open-field trial site established at the greenhouse of Karadeniz Technical University, Faculty of Forestry, in Trabzon.

Alchemilla mollis specimens were collected from an altitude of 1375 m at the coordinates 40°41′40.88″ N, 39°31′32.06″ E, on a southwest-facing slope in Anayurt Village, Maçka District, Trabzon. Similarly, Geranium psilostemon samples were gathered from the same elevation and slope direction, at the coordinates 40°41′40.08″ N, 39°31′32.62″ E, also within Anayurt Village, Maçka.

These sampling sites were selected based on preliminary field surveys aimed at identifying natural populations of A. mollis and G. psilostemon. Among the identified locations, sites with ease of access and sufficient individual density were prioritized. Special care was taken to ensure that the number of individuals collected would not significantly impact the local vegetation structure or ecological balance. The area where plant excavation was conducted is illustrated in Figure 1.

All necessary permissions for plant collection were obtained from the Republic of Türkiye Ministry of Agriculture and Forestry, General Directorate of Nature Conservation and National Parks, through the Biodiversity Research Permit System (permit No: E-21264211-288.04 [Biodiversity Research Permits]–1664441) (Figure 1).

The geographical location of the established perennial garden is between 40°59′36.64″ and 40°59′37.38″ N latitude and 39°46′40.15″ and 39°46′40.84″ E longitude. The site is situated at an elevation of 75 m above sea level, on a north-facing slope within the main campus of Karadeniz Technical University, specifically to the north of the Faculty of Forestry greenhouse (Figure 2).

2.2. Excavation of Native Plants from the Field

The excavation process was carried out during the dormancy period of the plants, specifically selected outside the active vegetation phase when physiological and morphological activities are minimal, and water consumption is at its lowest. This timing ensured minimal stress during uprooting and increased the likelihood of successful transplantation.

Accordingly, special attention was given to selecting perennial species from high-altitude regions after the completion of their flowering period. Another critical factor was the selection of individuals during the period between late August and November, when above-ground vegetative growth is visibly reduced. During this time, individuals were excavated from their natural habitats along with the surrounding soil.

During excavation, each plant was carefully dug out using a spade or a wide-blade mattock, starting from approximately 10 cm outside the canopy drip line, with a 360° soil cut around the root zone. The depth of excavation was adjusted based on the root system of each taxon. Extracted plants were either wrapped in root mesh or placed into nursery bags proportionate to the soil volume to prevent root ball disintegration during transport. For ground-covering species, rectangular soil blocks containing entire plant clusters were extracted using flat spades and placed into plastic crates to preserve root cohesion.

Throughout the excavation process, utmost care was taken to avoid damage to the native plant populations and their surrounding vegetation. In addition to native species, supplementary exotic plant taxa used in the study were obtained from commercial nurseries and transported to the site in containerized form.

The excavated and nursery-acquired plants were transported to the experimental area, located at an elevation of 75 m. Upon arrival, the plants were propagated through division and transplanted into pots and seedling bags. This propagation method aimed to obtain a sufficient number of individuals required for the experimental design.

The prepared pots were placed in a semi-shaded, wooded area where the plants would remain shaded during peak sunlight hours and receive limited exposure to sunlight in the late afternoon. In line with this, the selected area was leveled using an excavator, and a 40 cm-thick layer of river sand (mil) was spread over the surface. All potted and bagged individuals were then partially embedded (up to half their depth) into this sand layer along with their containers.

This setup provided a cool and protected environment for the seedlings, minimizing exposure to invasive species and extreme temperature fluctuations. The planted specimens were maintained in this semi-shaded area throughout the autumn and winter seasons to recover from transplant stress and to acclimate to the new growing conditions.

By the end of winter, individuals that had survived the acclimatization period, exhibited new leaf growth, and completed their establishment phase with minimal care were selected for planting. These viable individuals were then transferred to the experimental plots in accordance with the predefined trial design.

2.3. Design of Growing Media and Soil Analysis

2.3.1. Preparation of Growing Media

The study was conducted at the greenhouse facility of the Faculty of Forestry, located within the Kanuni Campus of Karadeniz Technical University (KTU). Written permission for the use of the site was obtained by submitting an official application to the KTU Faculty of Forestry Greenhouse Commission. The designated research site consisted of a flat open area located in front of the northern vehicle entrance of the greenhouse. All experimental procedures were carried out at this location.

To investigate the effects of different growing media, three distinct growing medium compositions were formulated. In this setup, the soil component was held constant, while river sand (mil) was treated as the variable. Accordingly, three media types were created by mixing the same soil with two different proportions of river sand.

The allocated area was leveled using a backhoe. Crushed gravel obtained from the Ortahisar Municipality Stone Crushing and Screening Facility (Konkasör facility, Trabzon, Türkiye) in Trabzon was spread over the surface to a depth of 10–15 cm to facilitate drainage.

To prepare the growing media, topsoil was supplied by the Department of Parks and Gardens of the Trabzon Metropolitan Municipality (Trabzon, Türkiye), and river sand was provided by the 22nd Regional Directorate of State Hydraulic Works (DSİ) (Trabzon, Türkiye), in accordance with the relevant permissions granted for this research.

The components of the growing media were prepared using a backhoe in an open area. During mixing, special care was taken to ensure homogeneity across all substrate compositions. Three distinct growing media were created by supplementing the base soil with two different proportions of river sand (mil). The mixture ratios were calculated based on volume.

• TA: 50% soil + 50% river sand;
• TB: 75% soil + 25% river sand;
• TC: 100% soil.

These media compositions were sequentially layered—beginning with TC, followed by TB and TA—over the gravel drainage layer in accordance with the spatial layout of the experimental plots.

2.3.2. Soil Analysis and Experimental Setup

Prior to the experiment, physical and chemical analyses were performed for each growing medium. In the designated plots, a total of 12 sampling points were determined by a random sampling method, ensuring one sample per growing medium per replicate. From each point, undisturbed soil samples were collected at a depth of 0–15 cm for analysis. This sampling process was conducted twice: once before transplanting (on 21 December 2021) and once at the conclusion of the study (on 20 August 2023).

The soil samples were analyzed for pH (1:2.5 soil:water suspension, measured with a glass electrode pH meter (Hanna Instruments, Temse, Belgium), electrical conductivity (EC) measured directly from undiluted soil using a Hanna Instruments HI98331 soil conductivity meter (Hanna Instruments, Temse, Belgium), total nitrogen (N) by the Kjeldahl method [50], organic matter (OM) using the Walkley–Black dichromate oxidation method [51], organic carbon (OC) by multiplying OM with 0.58 [52], and available phosphorus (P) using the Olsen method [53]. The soil analyses included measurements of pH, electrical conductivity (EC), total nitrogen (N), organic matter (OM), organic carbon (OC), and available phosphorus (P).

The collected soil samples were air-dried at room temperature for three days to facilitate sieving through a 2 mm mesh. To further ease the sieving process, the dried samples were gently ground using a porcelain mortar. They were then passed through 2 mm steel sieves, and the resulting soil fractions (<2 mm) were labeled, sealed in zipper bags, and prepared for laboratory analysis. Portions of these fine soil samples were sent to designated laboratories for specific analyses.

The soil analyses were conducted at the Soil Science Laboratory of the Atatürk Tea and Horticultural Research Institute. Electrical conductivity (EC) was measured as the average of three sampling points for each growing medium. EC measurements were carried out using a Hanna Instruments HI98331 model soil temperature and conductivity meter.

Electrical conductivity (EC), also referred to as electrical conductance, indicates the ability of a solution to conduct electrical current due to the presence of dissolved substances. It is expressed in milliSiemens per centimeter (mS/cm).

For planting, wooden border frames were prepared to form 30 cm × 30 cm grid units. Nails (3 mm in diameter) were hammered at 30 cm intervals along opposite sides of the wooden elements to ensure consistent spacing. Particular attention was given to maintaining 90° angles at the corners of each square (with a margin of error of ±2°). To prevent weed emergence prior to planting, the soil surface was covered with a ground cloth (weed barrier fabric).

The surviving and acclimatized plant individuals mentioned above were prepared for transplanting. Using colored string, 30 cm × 30 cm grid squares were marked on the growing media, and plants were planted in each grid cell in accordance with the experimental design. Prior to planting, all individuals were positioned with their seedling tubes intact directly in the assigned grid squares.

The experimental layout was established based on a completely randomized design with three replications. In each replication, 10 individuals of each species (A. mollis and G. psilostemon) were used.

A total of 90 individuals were planted for each species (3 growing media × 3 replications × 10 plants), resulting in 180 experimental plants overall.

2.4. Measurement of Plant Growth Parameters

Throughout the experiment, plant height, canopy diameter, leaf number, and chlorophyll content were measured at regular intervals to evaluate the growth performance of the two species. Measurements were taken monthly across 17 time points, including the dormant season when the plants were physiologically inactive.

All growth measurements were conducted in accordance with the standardized procedures detailed in the doctoral thesis of the first author [31]. Plant height was defined as the vertical distance from the root crown to the terminal bud of the tallest upright shoot, and canopy diameter was recorded as the maximum horizontal width of the plant’s foliage. Leaf number was determined through manual counting.

The chlorophyll content of the two native plant taxa used in this study was measured in units of µmol m⁻², which represents micromoles of chlorophyll per square meter of leaf area, as standardized by the Apogee MC-100 chlorophyll concentration meter (Apogee Instruments, Inc., Logan, UT, USA). These measurements were performed monthly for 15 months, excluding the two months when the plants were dormant belowground. Chlorophyll readings were taken using the Apogee MC-100 Chlorophyll Concentration Meter, a patented non-destructive device that accurately measures and displays chlorophyll content from intact leaf samples.

The device was set to the “GENERAL” calibration mode to provide chlorophyll concentration values in µmol of chlorophyll per square meter of leaf area. Care was taken to ensure that midribs were not positioned directly over the sensor window during measurement.

The chlorophyll content was measured in the following months:

• First growing season (2022): May (Month 1), June (2), July (3), August (4), September (5), October (6), November (7), December (8);
• Dead (Dormant) season (2023): January (9), February (10);
• Second growing season (2023): March (11), April (12), May (13), June (14), July (15), August (16), September (17).

Measurements were consistently taken from leaves on the same side of the plant to minimize variability.

2.5. Statistical Analyses

The collected data were analyzed using SPSS version 23.0. A two-way multivariate analysis of variance (MANOVA) was performed to examine the interaction effects between growing media (group) and time. In cases where significant differences were observed, post hoc comparisons were conducted using Tukey’s HSD test (p < 0.05) to evaluate differences among groups.

Prior to conducting the MANOVA, key assumptions were tested, including normality (via Shapiro–Wilk test), homogeneity of variance (via Levene’s test), and the absence of multicollinearity (checked through Pearson correlation coefficients). Box’s M test was used to assess the equality of covariance matrices. The significance level was set at 0.05.

Effect sizes (η²) were reported to indicate the strength of the observed effects.

2.6. Multi-Criteria Decision-Making (PROMETHEE) Analysis

To holistically assess the effects of different growing media on plant development, the PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluation) method was employed. This method allows simultaneous evaluation of multiple criteria from diverse perspectives such as plant performance, soil quality, and economic feasibility. A total of 11 evaluation criteria were used and categorized under three main perspectives: soil, plant, and economic (

Table 1. PROMETHEE evaluation criteria, weights, and preference functions.

Perspective	Criteria Number	Evaluation Criteria	Weight Value	Preference Function
Soil	C1	pH	0.10	Linear
	C2	Nitrogen (%)	0.10	V-shape
	C3	Organic matter (%)	0.09	V-shape
	C4	Organic carbon (%)	0.09	V-shape
	C5	Phosphate (mg/L)	0.09	Linear
	C6	Electrical conductivity (mS/cm)	0.09	V-shape
Plant	C7	Length (cm)	0.10	Linear
	C8	Diameter (cm)	0.10	Linear
	C9	Chlorophyll (µmol/m−2)	0.09	Linear
	C10	Number of leaves	0.08	Linear
Economic	C11	Cost (USD)	0.07	Linear

).

The PROMETHEE analysis was conducted individually for each species (A. mollis and G. psilostemon) to enable species-specific evaluation of growing media.

Following normalization, the data were analyzed using Visual PROMETHEE software (version 1.4, Université Libre de Bruxelles, Brussels, Belgium). All criteria were assigned the weight values shown in Table 1. Based on the resulting net flow values (φ), the performance of each growing medium was ranked to determine the most suitable substrate for both plant species.

2.7. Climatic Conditions of the Experimental Site

To characterize the climatic conditions of the experimental plots established at the Faculty of Forestry greenhouse of Karadeniz Technical University (KTU), monthly data were retrieved from the nearest meteorological station (Station No. 17037–Trabzon Region; coordinates: 40.9985° N, 39.7649° E, elevation: 25 m), provided by the Turkish State Meteorological Service. Data included average monthly maximum and minimum temperatures (°C), mean temperature (°C), total monthly precipitation (mm), and average relative humidity (%). These parameters were monitored across two growing seasons: 1 September 2021–31 August 2022 (Season 1) and 1 September 2022–31 August 2023 (Season 2).

During the first season, the annual mean temperature was 15.4 °C, and in the second season, it was 16.3 °C. August recorded the highest average temperatures in both years (26.4 °C). The coldest months were March (6.2 °C) in the first season and February (7.7 °C) in the second season. The highest recorded temperature was 29.5 °C in August 2023. Monthly temperature fluctuations were most pronounced in April 2022 (8.1 °C) and July 2023 (7.7 °C).

In terms of precipitation, the total annual rainfall was 865.6 mm in the first season and 813.2 mm in the second season, with the highest rainfall observed in the autumn (Season 1) and spring (Season 2). The driest periods were recorded during the summer months for both years.

Average relative humidity remained consistently high throughout the study period, with annual means of 69.9% and 69.3% in the first and second seasons, respectively. The highest monthly humidity was recorded in June 2022 (79.3%) and May 2023 (79.6%), while the lowest values were in December 2021 (57.4%) and January 2023 (58.9%).

Detailed monthly averages of temperature, precipitation, and relative humidity values recorded at the experimental site are presented in

Table 2. Monthly and annual averages of temperature (°C), precipitation (mm), and relative humidity (%) recorded at the Trabzon Region Meteorological Station (station No. 17037; 25 m elevation) for the two growing seasons (2021–2023).

Climate Variable	Season	Sep	Oct	Nov	Dec	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Annual Avg./Total
Monthly avg. max temperature (°C)	1	24.0	19.2	18.4	15.2	11.0	12.8	8.9	18.0	18.5	24.2	26.3	29.4	18.8
	2	25.9	20.7	18.6	15.4	13.3	11.1	14.2	17.4	18.3	24.3	28.1	29.5	19.7
Monthly avg. min temperature (°C)	1	17.7	13.1	11.1	8.4	5.0	6.7	3.9	9.9	12.4	19.0	20.5	23.9	12.6
	2	18.9	15.0	12.3	9.7	6.6	4.9	8.3	10.5	12.9	18.8	20.4	23.1	13.5
Monthly avg. temperature (°C)	1	20.3	15.9	14.3	11.3	7.7	9.6	6.2	13.5	15.2	21.3	23.2	26.4	15.4
	2	22.4	17.5	15.2	12.2	9.6	7.7	10.7	13.5	15.3	21.4	24.1	26.4	16.3
Monthly total precipitation (mm = kg÷m2)	1	130.0	80.6	50.4	107.6	117.2	24.4	107.4	47.0	62.8	75.8	26.8	35.6	865.6
	2	96.8	57.8	34.4	73.6	34.8	115.4	63.8	128.0	69.6	69.8	56.2	13.0	813.2
Monthly avg. relative humidity (%)	1	74.2	75.4	69.0	57.4	62.8	64.7	72.0	65.9	73.1	79.3	68.9	76.4	69.9
	2	65.9	73.8	65.6	66.3	58.9	60.8	75.3	71.2	79.6	79.3	65.5	70.0	69.3

Season 1: Sep 2021–Aug 2022, Season 2: Sept 2022–Aug 2023.

.

3. Result

3.1. Morphological Growth Performance and Soil Parameter Findings

In this study, the growth performance of Alchemilla mollis and Geranium psilostemon was evaluated under low-altitude environmental conditions across three different soil–sand (mil) mixtures (TA, TB, TC). Morphological parameters—plant height, canopy diameter, chlorophyll content, and leaf count—were monitored monthly for both species and statistically analyzed using MANOVA tests.

Figure 3 illustrates the temporal changes in plant height, canopy diameter, number of leaves, and chlorophyll content for A. mollis and G. psilostemon. In both species, the overall growth trends appear to be influenced by seasonal transitions. Notably, a physiological stagnation period was observed between months 8 and 10. This phase, marked as the “dead season” with purple lines in the figure, corresponds to a period in which the plants maintained belowground development while aboveground biomass was either dormant or necrotic.

For Alchemilla mollis, plant height measurements indicated that individuals grown in the TC growing medium exhibited a notable increase in growth after the 13th month, reaching approximately 35 cm by month 16. Slower and more limited growth was observed in the TA and TB media. Regarding canopy diameter, the TC and TB growing media produced similar values starting from the 13th month, while plants in the TA medium consistently lagged behind. Among these, the highest average canopy diameter was recorded in the TB medium.

An upward trend in leaf count was observed after the 10th month. While all growing media exhibited similar increases, plants grown in the TC medium stood out, reaching approximately 45 leaves by the 15th month. As for chlorophyll content, A. mollis in the TC growing medium exhibited a rapid recovery following a seasonal decline, with levels surpassing 270 µmol m⁻². In contrast, chlorophyll levels remained lower in the TB medium.

For Geranium psilostemon, plant height in the TC medium showed a sharp increase approaching the 16th month, whereas the TA medium demonstrated substantially weaker growth performance. In terms of canopy diameter, the TB and TC growing media were associated with superior development, while the TA medium again yielded the lowest values. Leaf number increased significantly after the ninth month, with the TC medium producing the best results—reaching up to 35 leaves between months 14 and 16.

The highest average chlorophyll content for G. psilostemon was also observed in the TC growing medium, where values reached approximately 350 µmol m⁻² according to the analyses.

In the case of Alchemilla mollis, the variance analysis revealed that the time factor had a statistically significant effect on all measured growth parameters (p < 0.01). Plant height (F = 20.38; η² = 0.607), canopy diameter (F = 15.80; η² = 0.545), chlorophyll content (F = 7.90; η² = 0.375), and number of leaves (F = 11.19; η² = 0.459) all showed significant increases over time (

Table 3. Statistical evaluation of morphological and physiological growth parameters based on plant bed and time.

Species	Parameters	Source of Variance	Sum of Squares	Mean Square	F	η2	p
Alchemilla mollis	Length	Group	79.91	39.95	0.84	0.013	>0.05
		Time	9725.77	972.58	20.38	0.607	<0.01
		Group × Time	2184.63	109.23	2.29	0.258	<0.01
		Error	6298.00	47.71
	Diameter	Group	41.68	20.84	0.25	0.004	>0.05
		Time	12,859.50	1285.85	15.80	0.545	<0.01
		Group × Time	1949.78	97.49	1.19	0.154	>0.05
		Error	10,743.20	81.39
	Chlorophyll	Group	3257.01	1628.51	1.37	0.020	>0.05
		Time	94,100.94	9410.09	7.90	0.375	<0.01
		Group × Time	72,891.17	3644.56	3.06	0.317	<0.01
		Error	157,125.70	1190.35
	Number of leaf	Group	900.16	450.08	2.39	0.035	>0.05
		Time	21,076.30	2107.63	11.19	0.459	<0.01
		Group × Time	1635.04	81.75	0.434	0.062	>0.05
		Error	24,843.20	188.21
Geranium psilostemon	Length	Group	782.59	391.29	1.60	0.024	>0.05
		Time	30,817.39	2801.58	11.44	0.496	<0.01
		Group × Time	5734.18	318.56	1.30	0.155	>0.05
		Error	31,336.00	244.81
	Diameter	Group	1684.48	842.24	6.57	0.093	<0.01
		Time	28,480.22	2589.11	20.20	0.634	<0.01
		Group × Time	2267.79	125.98	0.98	0.121	>0.05
		Error	16,406.40	128.17
	Chlorophyll	Group	183,885.91	91,942.96	126.40	0.664	<0.01
		Time	283,954.24	25,814.02	35.49	0.753	<0.01
		Group × Time	139,091.51	7727.31	10.62	0.599	<0.01
		Error	93,105.99	727.39
	Number of leaf	Group	158.48	79.24	0.49	0.008	>0.05
		Time	14,721.95	1338.36	8.38	0.419	<0.01
		Group × Time	3851.51	213.97	1.34	0.159	>0.05
		Error	20,444.40	159.72

).

When comparing across growing media, the group factor alone did not exhibit a statistically significant effect on any of the parameters (all p > 0.05). However, for chlorophyll content, the group factor approached marginal significance (F = 1.37; η² = 0.020), with the highest chlorophyll values observed in the TC growing medium.

The interaction between time and group (Group × Time) was statistically significant for plant height (F = 2.29; p < 0.01) and chlorophyll content (F = 3.06; p < 0.01). This suggests that the influence of different growing media on plant development varied over time. However, the interaction was not significant for canopy diameter and leaf number.

For Geranium psilostemon, statistical analyses also revealed that the time factor had a highly significant effect on all measured parameters. Plant height (F = 11.44; η² = 0.496), canopy diameter (F = 20.20; η² = 0.634), chlorophyll content (F = 35.49; η² = 0.753), and number of leaves (F = 8.38; η² = 0.419) all showed statistically significant increases over time (p < 0.01).

Among the different growing media, the most pronounced variation was observed in chlorophyll content. The group factor had a highly significant effect on this parameter (F = 126.40; p < 0.01; η² = 0.664), indicating that the composition of the soil–sand mixtures strongly influenced the photosynthetic capacity of G. psilostemon. Canopy diameter was also significantly affected by the group factor (F = 6.57; p < 0.01), with higher mean values observed in the TA group in particular.

The interaction between time and group was statistically significant only for chlorophyll content (F = 10.62; p < 0.01; η² = 0.599), suggesting that the influence of growing media on this parameter varied over time. For the other parameters, the Group × Time interaction was not statistically significant.

These findings indicate that differences in the soil–sand ratio are particularly influential on chlorophyll production and plant height. Soil analyses conducted at the beginning and end of the experiment revealed significant changes in the physicochemical properties of the different soil–sand mixtures. For both plant species, the lowest pH values were recorded in the TC growing medium, while the highest values were observed in TA. This indicates that increasing the proportion of sand resulted in lower pH values, thereby creating a more acidic growing environment (p < 0.05). This difference was statistically significant in the final measurements, following the pattern TA > TB > TC (

Table 4. Comparison of plant bed groups in terms of soil quality parameters. Lower case represents statistical differences between groups based on one-way ANOVA.

Alchemilla mollis
		TA	TB	TC
pH	Initial	7.00 ± 0.70 a	6.59 ± 0.30 ab	5.87 ± 0.12 b
	Final	6.79 ± 0.24 a	6.53 ± 0.08 ab	6.11 ± 0.19 b
N%	Initial	0.05 ± 0.01	0.04 ± 0.02	0.05 ± 0.02
	Final	0.03 ± 0.03	0.09 ± 0.07	0.06 ± 0.03
OM%	Initial	1.00 ± 0.00	1.00 ± 0.00	0.90 ± 0.20
	Final	0.60 ± 0.70	1.83 ± 1.53	1.13 ± 0.50
OC%	Initial	0.58 ± 0.12	0.50 ± 0.17	0.59 ± 0.21
	Final	0.36 ± 0.39	1.05 ± 0.86	0.65 ± 0.33
P	Initial	9.00 ± 7.00	37.0 ± 32.9	20.7 ± 20.1
	Final	22.36 ± 18.2	76.19 ± 61.3	67.41 ± 47.8
EC	Initial	0.06 ± 0.02	0.12 ± 0.09	0.08 ± 0.04
	Final	0.06 ± 0.02	0.05 ± 0.03	0.06 ± 0.04
Geranium psilostemon
		TA	TB	TC
pH	Initial	7.07 ± 0.61 a	6.66 ± 0.40 ab	5.84 ± 0.15 b
	Final	6.80 ± 0.25 a	6.50 ± 0.06 ab	6.18 ± 0.27 b
N%	Initial	0.04 ± 0.02	0.05 ± 0.02	0.04 ± 0.03
	Final	0.06 ± 0.04	0.11 ± 0.05	0.08 ± 0.02
OM%	Initial	1.00 ± 0.00	1.00 ± 0.00	0.73 ± 0.46
	Final	1.10 ± 0.89	2.23 ± 0.86	1.53 ± 0.38
OC%	Initial	0.50 ± 0.24	0.54 ± 0.18	0.53 ± 0.31
	Final	0.65 ± 0.51	1.27 ± 0.49	0.89 ± 0.21
P	Initial	9.33 ± 6.66	36.67 ± 33.3	22.33 ± 18.1
	Final	23.31 ± 17.4	75.42 ± 62.5	67.87 ± 47.1
EC	Initial	0.08 ± 0.06	0.06 ± 0.05	0.02 ± 0.01
	Final	0.07 ± 0.03	0.05 ± 0.02	0.11 ± 0.08

).

Regarding total nitrogen content (N%), a notable increase was observed in the TB growing medium for Alchemilla mollis, where values initially ranging from 0.04–0.05% reached up to 0.09% by the end of the study. A similar trend was observed for G. psilostemon, with the highest nitrogen content (0.11%) also measured in the TB medium. This suggests that the 75% soil composition in TB provided a greater nitrogen-retention capacity compared to the other mixtures. At the end of the experiment, both organic matter (OM%) and organic carbon (OC%) contents reached their highest levels in the TB growing medium for both species. For G. psilostemon, OM increased to 2.23% and OC to 1.27%. These results suggest that the TB medium supports organic matter accumulation and carbon enrichment more effectively than the other treatments (Table 4). With regard to available phosphorus (P), substantial increases were recorded for both Alchemilla mollis and Geranium psilostemon compared to pre-experiment values. Notably, in the TB growing medium, the final phosphorus levels reached 76.19 mg/kg for A. mollis and 75.42 mg/kg for G. psilostemon, more than doubling the initial concentrations. This increase likely reflects the impact of the soil–sand composition on phosphorus retention and release capacity.

For the electrical conductivity (EC) parameter, no major differences were observed overall. However, for G. psilostemon, EC levels in the TC growing medium increased significantly by the end of the study, reaching 0.11 mS/cm. This suggests that a higher soil proportion may lead to the accumulation of dissolved salts in the medium. Taken together, these findings indicate that the TB medium is more effective at retaining key nutrients such as organic matter and nitrogen, whereas the TC medium offers a more acidic environment due to its lower pH. Each medium presents distinct advantages, and the selection of growing substrates should therefore be guided by the specific species and desired outcomes of cultivation.

3.2. PROMETHEE Multi-Criteria Decision-Making (MCDM) Findings

The criteria were normalized to ensure a total weight of 1. The highest weights (10% each) were assigned to pH, nitrogen content, plant height, and canopy diameter. Chlorophyll content and organic matter were assigned weights of 9%, leaf number 8%, and economic cost 7%. Preference functions were defined as either linear or V-shaped, depending on the nature of each criterion. This structure allowed for the harmonized comparison of variables with different measurement scales (Figure 4).

According to the PROMETHEE analysis, the TC growing medium (100% soil) demonstrated the highest overall performance for both plant species and was ranked first (

Table 5. Net preference flow (φ) values and rankings of growing media according to PROMETHEE analysis.

	Groups	φ+ (i)	φ− (i)	φ (i)	Ranks
Alchemilla mollis	TC	0.5273	0.1005	0.4268	1
	TB	0.3383	0.1579	0.1805	2
	TA	0.0452	0.0452	0.0452	3
Gerranium psilestemon	TC	0.5511	0.0963	0.4548	1
	TB	0.2677	0.2343	0.0335	2
	TA	0.0910	0.5792	−0.4882	3

). This medium provided the most balanced and favorable outcomes in terms of both soil characteristics and plant development:

For Alchemilla mollis

• φ⁺ = 0.5273;
• φ⁻ = 0.1005;
• φ (net flow) = 0.4268;
• Rank = 1.

For Geranium psilostemon

• φ⁺ = 0.5511;
• φ⁻ = 0.0963;
• φ (net flow) = 0.4548;
• Rank = 1.

The TB growing medium (75% soil + 25% sand) ranked second in the PROMETHEE analysis despite having lower net flow (φ) values. While this substrate exhibited strong performance in certain criteria—particularly nitrogen content and organic matter—it fell behind the TC medium in terms of overall effectiveness.

• A. mollis: φ = 0.1805;
• G. psilostemon: φ = 0.0335.

The TA growing medium (50% soil + 50% sand) ranked last, especially for G. psilostemon, which exhibited a negative net flow (φ = −0.4882). This result indicates that a higher proportion of sand may compromise the physical and chemical properties of the growing medium, making it less suitable for plant development.

The PROMETHEE criteria contribution chart (Figure 4) revealed that plant growth parameters contributed the most to the overall ranking, followed by soil quality indicators and, lastly, economic cost. Specifically, chlorophyll content, plant height, and canopy diameter were found to have the most significant impact on the φ net flow values. These results demonstrate that growing media with a higher proportion of soil (such as TC) are more effective not only in promoting physiological growth but also in achieving better outcomes from environmental and economic perspectives.

4. Discussion

4.1. Effect of Growing Media on Morphological Development

In this study, the morphological growth parameters of Alchemilla mollis and Geranium psilostemon were evaluated under low-altitude conditions using three different soil–sand (mil) mixtures (50% soil + 50% sand, 75% soil + 25% sand, and 100% soil). The results demonstrated that the growing medium had a significant effect on plant development. In particular, the TC medium (pure soil) consistently yielded the highest average values for both plant height and chlorophyll content across both species (Table 3). Direct comparisons among treatments revealed that the TC medium showed the most pronounced positive effect on both species’ height and chlorophyll concentration, especially after the mid-experimental period.

These superior growth outcomes in the TC medium may be attributed to its high water-holding capacity and improved aeration around the root zone. Previous studies have emphasized the critical role of soil structure in guiding root development and supporting above-ground biomass accumulation [37,38,39,54]. Similarly, Karadavut et al. (2019) highlighted that well-aerated and organic matter-rich soils enhance overall plant performance [32].

In the present study, a marked acceleration in growth was observed in TC-grown individuals beginning in the 13th month, with peak values reached by month 16. This suggests that the TC medium offered a more resilient and sustainable growth profile under post-transplant stress conditions (Figure 3). The rapid growth pattern observed in the statistical tables also indicates that morphological development accelerated after the plants adapted to the experimental environment. Moreover, the climatic conditions recorded at the experimental site during the trial period provide valuable context for interpreting plant performance. The relatively mild average temperatures (15.4–16.3 °C) and high relative humidity levels (approximately 69–70%) throughout the two-year observation period likely contributed to stable root zone moisture and reduced evapotranspiration stress. These conditions may have supported consistent physiological functioning, particularly in TC media, where enhanced water retention aligned well with the humid, temperate microclimate of the study site. The high August temperatures (up to 29.5 °C) may explain the peak chlorophyll values and rapid vegetative expansion observed during the summer months.

Regarding canopy diameter, it was noted that the TB growing medium occasionally achieved values comparable to those in TC, particularly in Geranium psilostemon, where a more uniform spread pattern was observed. This may be related to the moderate sand content in TB, which optimized both drainage and nutrient retention.

Canopy development in plants is influenced not only by soil structure but also by the water-holding capacity of the medium, the distribution of micronutrients, and the aeration of the root zone. Growing media that provide a balanced combination of permeability and organic matter content tend to support lateral (horizontal) expansion, resulting in more homogeneous and balanced crown architecture [55,56,57].

The number of leaves reached its highest values in the TC growing medium. In contrast, the low development observed in Geranium psilostemon under the TA growing medium suggests that this species is more sensitive to higher proportions of sand. This supports the view that G. psilostemon demonstrates phenotypic plasticity under favorable conditions (e.g., nutrient-rich TC), whereas its performance declines sharply in more stressful conditions such as the TA substrate. A. mollis, on the other hand, displayed more consistent development across treatments, highlighting its stress resilience and suitability for challenging urban environments.

Chlorophyll concentrations were also considerably higher in the TC medium compared to the others. Krause and Weis (1991), Arısoy (2023), Yuan et al. (2023), and Ashraf and Harris (2013) have noted that chlorophyll content is a key indicator of photosynthetic capacity and can be directly used to assess plant health [43,44,58,59].

Furthermore, leaf production and quantity are not only dependent on photosynthetic efficiency but are also closely linked to the availability of water and nutrients in the rhizosphere. Growing media with well-structured soil and high organic matter content promote vigorous leaf development, thereby enabling plants to attain a denser and healthier form [60,61,62].

The findings of this study support these perspectives and indicate that optimal morphological performance was achieved in growing media with higher soil content. The statistically significant interaction effects (Group × Time) observed in chlorophyll content and plant height (Table 3) emphasize the importance of temporal dynamics in assessing plant responses to substrate composition. Such interaction effects, when interpreted agronomically, suggest that long-term cultivation in nutrient-balanced media enhances adaptive morphological traits.

The results demonstrate that both species-specific morphological responses and the applied soil–sand ratios significantly influenced plant development. These results suggest that future perennial planting designs should consider substrate composition not only for immediate establishment but also for long-term morphological stability and physiological optimization.

These insights provide a strong foundation for the use of native plant materials in landscape applications.

4.2. Changes in Soil Parameters and Their Interaction with Plants

Soil analyses conducted at the beginning and end of the experiment revealed critical findings. Over time, distinct chemical and physical changes were observed in the soil structure as a result of interactions with the plants grown in different soil–sand mixtures (Table 4). Regarding pH values, the TC growing medium (100% soil) showed the lowest pH levels for both Alchemilla mollis and Geranium psilostemon. This indicates that higher proportions of sand lead to a more basic medium, while increasing the soil proportion results in a more acidic environment. The final pH values showed statistically significant differences among growing media, following the pattern TA > TB > TC (p < 0.05).

Soil pH is a key factor that directly affects plant access to nutrients. The availability of essential elements such as iron, phosphorus, and zinc is highly sensitive to pH fluctuations. Therefore, maintaining pH within the optimal range is crucial for healthy plant growth [33,63,64,65]. This finding aligns well with the morphological development results observed in this study and helps explain the balanced growth performance associated with the TC growing medium.

In contrast, nitrogen (N%) and organic matter (OM%) content showed notable increases in the TB growing medium. For G. psilostemon, the nitrogen content in TB rose from 0.05% at the beginning of the experiment to 0.11% by its conclusion. This increase suggests that the mixture containing 75% soil and 25% sand better supported microbial activity and nutrient mineralization compared to other media.

Temel and Keskin (2019) reported that soils rich in organic matter enhance microbial activity, thereby accelerating the nitrogen cycle and promoting plant growth [66]. Increased microbial activity in the soil speeds up nitrogen cycling, particularly through mineralization processes, which convert organic nitrogen into plant-available forms such as nitrate (NO₃⁻) and ammonium (NH₄⁺). This mechanism is especially prominent in organic matter-rich soils and forms the basis of biological productivity and effective plant nutrition [67,68,69]. In line with this, the TB growing medium supported higher OM% and OC% accumulation compared to TA and TC, providing a fertile environment for physiological development.

A similar trend was observed in the TB medium in terms of organic carbon (OC%) content. When phosphorus (P) levels in the TB and TC growing media were examined, both plant species exhibited substantial increases compared to the beginning of the experiment. This increase is likely related to the release of phosphorus during the decomposition of organic matter.

Studies by Yusran (2005), Hawkins et al. (2022), and Salas et al. (2003) have demonstrated that as organic matter decomposes in the soil, it facilitates the transformation of phosphorus into more plant-available forms, resulting in significantly elevated P levels over time [70,71,72]. In the present study, this was particularly evident in the TB medium, where phosphorus levels for Alchemilla mollis reached as high as 76.19 mg/L.

On the other hand, although electrical conductivity (EC) values did not show substantial fluctuations overall, a significant increase (0.11 mS/cm) was recorded in the TC growing medium for Geranium psilostemon by the end of the experiment. This rise in EC observed in the TC medium can be attributed to the higher soil content, which tends to retain more dissolved ions. The finding is consistent with previous research indicating that both organic and inorganic fractions influence ion solubility and can lead to increased EC values over time [39,73,74].

These studies suggest that the accumulation of dissolved ions in the soil elevates EC values, which, in turn, may influence plant development. In the present study, the chemical changes in the soil were reflected in key physiological indicators such as chlorophyll content and leaf number. These results demonstrate that different soil–sand ratios not only affect the physical growth of the plant but also play a crucial role in shaping the chemical environment of the root zone.

Notably, the TB growing medium stood out for its balanced nutrient availability, owing to its elevated nitrogen and organic matter content. This suggests its potential as a favorable substrate for sustainable plant cultivation. While TC promoted acidification and biomass growth, TB supported nutrient cycling, positioning it as a reliable substrate option when moderate input and sustainability are prioritized. These findings offer practical guidance for substrate selection in urban perennial gardens.

4.3. Effect of Growing Media According to PROMETHEE Analysis

In this study, a broader evaluation approach was adopted by applying the PROMETHEE model, a multi-criteria decision-making method that goes beyond plant growth and soil parameter assessments alone. The PROMETHEE model provides a multidimensional perspective to the decision-making process by considering both positive (φ⁺) and negative (φ⁻) preference flows in the analysis of alternatives.

This feature makes PROMETHEE particularly effective in fields that require complex decision-making, such as agriculture, environmental engineering, and landscape design. The literature also emphasizes the flexibility and user-friendliness of PROMETHEE compared to other MCDM techniques, especially due to its ability to incorporate both quantitative and qualitative criteria [45,47,48].

In the PROMETHEE analysis, 11 criteria were evaluated simultaneously (Table 1). These criteria were grouped under three main perspectives: soil properties, plant growth performance, and economic feasibility. The criteria under these three main categories were integrated into the model with assigned weight values. The highest weights (0.10) were allocated to key soil and morphological criteria such as pH, nitrogen content, plant height, and canopy diameter, while chlorophyll content, organic matter, and organic carbon were assigned slightly lower but still significant weights of 0.09. Through this multi-criteria model, the objective was to move beyond solely assessing growth performance and to establish a more comprehensive decision-support framework.

Unlike single-parameter comparisons, this approach enabled more integrated comparisons between the three growing media (TA, TB, TC) by capturing their cumulative performance across biological, ecological, and economic dimensions.

Based on the resulting net flow values (φ), the TC growing medium exhibited the highest overall performance for both species. It ranked first for Alchemilla mollis (φ = 0.4268) and Geranium psilostemon (φ = 0.4548). In contrast, the TA growing medium yielded the lowest performance, particularly for G. psilostemon, with a negative net flow (φ = −0.4882), indicating substantially poor suitability.

These rankings were derived from individual PROMETHEE analyses conducted separately for each species, thereby allowing species-specific prioritization of substrate alternatives.

These findings highlight that growing media with higher soil proportions not only enhance physical plant development but also contribute positively to sustainability, photosynthetic efficiency, and overall soil health. Angers and Caron (1998) and Sharma and Kumar (2023) have indicated that soil structure not only influences physical growth but also enhances plant physiological activity [75,76]. Similarly, Rillig and Mummey (2006) and Bengough (2003) emphasized a positive relationship between soil health and plant physiological functions in their respective studies [77,78].

While PROMETHEE effectively synthesized diverse variables into an actionable framework, one limitation of this model in biological studies is its static assignment of weight values, which may not fully reflect dynamic ecological interactions.

Nevertheless, PROMETHEE enabled a transparent and quantifiable evaluation of substrate suitability—demonstrating, for example, how TC supported superior chlorophyll content and biomass growth, while TB optimized nutrient retention.

The findings of the present study demonstrate that decision-makers can make informed and multidimensional choices based not only on biological performance but also on factors such as soil fertility, application cost, and environmental impact. Therefore, supporting PROMETHEE-based decision models with experimental data of this kind improves the quality of scientific decision-making processes and facilitates the management of complex variables encountered in practical applications.

4.4. The Role of Findings in Sustainable Landscape Design and Perennial Plant Selection

The successful cultivation of high-altitude species such as Alchemilla mollis and Geranium psilostemon under low-altitude conditions demonstrates their potential to contribute both aesthetically and functionally to landscape design. The strong performance of growth parameters—including plant height, leaf count, and chlorophyll content—supports the notion that these species possess robust adaptability to environmental stressors.

Gitelson et al. (2006) and Houborg et al. (2013) noted that leaf chlorophyll content within the range of approximately 0.8–1.5 µmol m⁻² enhances the carbon sequestration capacity at the ecosystem level, thereby contributing positively to environmental sustainability [79,80].

Moreover, the use of native plant species in landscape architecture not only improves visual quality but also delivers key ecosystem services such as microclimate regulation, carbon retention, and habitat integrity due to their compatibility with local climate and soil conditions [81,82,83]. In this context, the use of native perennial species is understood to offer not only ecological but also economic advantages, such as reduced water consumption and lower maintenance costs, thus making significant contributions to sustainable urban landscapes. Numerous studies on native plant species support this finding [84,85,86].

The present findings highlight that A. mollis exhibits greater resilience under resource-limited or stress-prone conditions, while G. psilostemon demonstrates higher phenotypic plasticity under favorable growing environments. This differential behavior should be considered when selecting substrates and microhabitats for perennial garden design.

Furthermore, studies by Oz et al. (2016) and Şöhretoğlu et al. (2010) have reported the traditional medicinal use of Alchemilla mollis and Geranium psilostemon, respectively [87,88]. The traditional medicinal relevance of these species suggests that their value extends beyond ornamental functions in landscape design and underscores their role in preserving cultural heritage and biological diversity.

The results of the PROMETHEE analysis further reveal that parameters such as economic feasibility and soil health should be considered alongside plant growth when evaluating plant species for landscape applications. In this regard, the study presents a holistic evaluation framework that integrates multiple dimensions of landscape sustainability.

Additionally, this research provides practical insights for substrate selection based on species-specific responses. For example, the TC medium is more suitable for maximizing physiological growth, while TB supports nutrient accumulation. Designers may thus tailor growing media depending on whether rapid canopy development or long-term soil enrichment is prioritized.

Moreover, testing different ratios of soil and sand in the growing media provides a scientific foundation for identifying optimal substrate compositions. This will facilitate the planning of resource-efficient, environmentally compatible design solutions, particularly within urban settings. According to Smetana and Crittenden (2014), Castro et al. (2014) and Minaz (2024), the use of growing media compatible with the nutritional needs of plants in planting and design applications can reduce water consumption and facilitate the development of ecologically valuable landscape designs [86,89,90].

Future research should aim to replicate this experimental model across varying climatic zones and urban contexts. Evaluating additional substrate components (e.g., compost, biochar) and expanding the number of growing seasons would enhance the generalizability of the findings and provide further refinement for ecological landscape planning.

In conclusion, this study not only evaluated the growth of two perennial species but also assessed the broader potential of native plants in landscape architecture through a multidimensional approach. The integration of such scientific data into decision-making processes is essential for creating sustainable, aesthetically pleasing, and functional landscape environments. Furthermore, it plays a vital role in maintaining ecological balance and guiding environmentally responsible planning for the future.

5. Conclusions

This study comparatively examined the growth performance of two high-altitude native plant species—Alchemilla mollis and Geranium psilostemon—in a low-altitude environment using different soil–sand (mil) mixtures. The findings provide data-driven insights for the use of these species in landscape applications. The results revealed that the growing medium composed of 100% soil (TC) offered the highest performance in terms of both morphological development and photosynthetic capacity. Additionally, the TB growing medium (75% soil–25% sand) demonstrated superior outcomes particularly in terms of organic matter accumulation and nitrogen content.

These findings suggest that TC medium is more suitable for optimizing above-ground biomass and chlorophyll density, especially for G. psilostemon, while TB medium is recommended for nutrient retention and soil quality improvement, particularly for A. mollis.

Therefore, species-specific substrate recommendations can be made for perennial garden practices: TC for rapid growth and foliage expression, and TB for soil enrichment and stress resilience.

The multi-criteria decision-making process, supported by PROMETHEE analysis, provided a comprehensive perspective by evaluating not only morphological parameters but also soil health and economic feasibility—covering a total of 11 criteria. This approach offered a more integrated assessment for sustainable landscape planning.

Furthermore, the PROMETHEE model proved to be an effective tool in supporting practical horticultural decisions by synthesizing physiological, ecological, and economic indicators into a single decision framework. However, it is worth noting that the model’s static weighting assumption may limit its adaptability in highly dynamic biological systems.

Species-wise comparisons indicated that A. mollis exhibited more stable development and greater resilience to environmental stress, while G. psilostemon responded with rapid and robust physiological growth when favorable conditions were met. This highlights the importance of selecting plant species in landscape design not only based on aesthetic or functional considerations but also on their ecological tolerance and adaptability.

From the standpoint of sustainable landscape practices, this study clearly demonstrates that native perennial species not only offer visual appeal but also contribute significantly to ecological functionality and environmental resilience. Based on the research findings, prioritizing native and locally adapted plant species over exotic ones in urban landscapes—and demonstrating their successful cultivation under suitable growing media—provides a strong scientific foundation for design strategies aligned with sustainability goals.

The inclusion of native perennials with low maintenance and high environmental compatibility also holds potential economic benefits for cities, such as reduced irrigation demands, fewer chemical inputs, and longer plant lifespans. Moreover, comparing these results with commercial potting substrates or conventional soil mixes in future trials would offer a clearer baseline for real-world urban applications.

Future research should expand the scope of this approach by incorporating a wider range of plant species and climate zones. Additionally, longitudinal trials across multiple growing cycles and alternative substrate compositions will further validate these findings and help refine substrate selection strategies for urban perennial gardens. Replicating such studies in diverse urban microclimates or across biogeographical regions will strengthen the applicability of native plant-based landscape solutions.