Mulching is a sustainable agronomic practice that can improve soil quality and fruit characteristics in crops. This study investigated the influence of sheep wool mulch and a soil conditioner on growth, the accumulation of bioactive compounds, and soil enzymatic activity in apple orchards. A two-year field experiment (2023–2024) was conducted using three experimental methods: mulching with sheep wool (V2), application of a soil conditioner, corn starch-based polymer (V3), and a combination of sheep wool and corn starch-based polymer (V4) along with a control (V1). Tree growth parameters, fruit physicochemical properties, total phenolic and flavonoid content, and soil enzyme activities (dehydrogenase, catalase, phosphatase) were assessed. Data were analyzed using Principal Component Analysis (PCA) and Pearson’s correlation. PCA showed that the combined variant (V4) improved fruit size, weight, and bioactive compound content, while wool mulch alone (V2) was associated with higher fruit yield and better vegetative growth. Catalase activity correlated positively and consistently with bioactive compounds in both years, while phosphatase activity showed an intensified positive relationship in 2024. Dehydrogenase activity was negatively correlated with phenolic content in both seasons. Organic and integrated mulching practices can beneficially modulate both aboveground and belowground plant–soil interactions. The combined variant proved to be the most effective strategy, enhancing fruit nutritional quality and supporting sustainable apple orchard management.

Polygonum aviculare L. (PAV) is a widely distributed medicinal plant traditionally used for its diuretic, anti-inflammatory, and antioxidant properties, whose phenolic composition varies with provenance. This study provides the first integrated pharmacobotanical and phytochemical characterization of five wild PAV populations collected across a lowland-to-mountain gradient (105–605 m a.s.l.) in Bihor County, northwestern Romania. Botanical identity was authenticated by macroscopic and microscopic pharmacobotanical examination, which revealed a consistent anatomical organization alongside a qualitative morphological gradient related to altitude. The phenolic profile of the aerial parts was determined by HPLC-DAD-ESI-MS, and differences among populations were assessed by one-way ANOVA with Tukey’s HSD test. Fourteen phenolic compounds were detected and annotated, comprising one hydroxycinnamic acid, twelve flavonol glycosides, and one flavonol aglycone, with kaempferol derivatives predominating across all populations. Chlorogenic acid and rutin were confirmed using authentic reference standards, whereas the remaining compounds were tentatively annotated. A quercetin-O-arabinoside tentatively assigned as avicularin was consistently detected across all populations, supporting its potential as a candidate phytochemical marker. The sum of chromatographically quantified phenolic compounds varied markedly, showing a nearly six-fold difference between the richest and poorest populations, while the qualitative fingerprint remained conserved. Exploratory analysis indicated a general tendency toward lower phenolic content along a lowland-to-mountain environmental gradient characterized by increasing altitude and precipitation and decreasing mean annual temperature, although the total content was not significantly correlated with altitude. This pronounced inter-population variability underlines that wild-harvested PAV cannot be assumed uniform, highlighting the need for standardized extracts and site-specific phytochemical documentation in its pharmaceutical use.