This article is devoted to some aspects of the fragrant substances of plant origin applied in the food industry and perfumery as well. Since antiquity many extractive techniques have been developed to obtain essential oils. Some of them are still applied, but new ones, like microwave or ultrasound-assisted extractions, are more and more popular and they save time and cost. Independently of the procedure, the resulting essential oils are the source of many so-called isolates. These can be applied as food additives, medicines, or can be used as starting materials for organic synthesis. Some substances exist in very small amounts in plant material so the extraction is not economically profitable but, after their chemical structures were established and synthetic procedures were developed, in some cases they are prepared on an industrial scale. The substances described below are only a small fraction of the 2000–3000 fragrant molecules used to make our life more enjoyable, either in food or perfumes. Additionally, a few examples of allelopathic fragrant compounds, present in their natural state, will be denoted and some of their biocidal features will be mentioned as an arising “green” knowledge in agriculture.

Agricultural production is a crucial part of policy issue in preventing depopulation of mountainous areas across Europe. However, soil and climate conditions are limiting yields and profitability of crop production in these regions. The European Union (EU) subsidizes agriculture in mountains by special payments (Less Favoured Area (LFA) subsidy) when areas match law-specified natural handicaps. This study aims to assess whether LFA subsidy in Poland is sufficient to cover losses caused by lower yields of crops cultivated in a mountainous region of Poland (Low Beskid Mountains in Carpathians) compared to lowland regions (non-LFA areas). The results indicated that LFA subsidy was adequate for crops (facultative wheat, winter wheat, field bean and spring barley) grown in the years 2015–2018.

Cultivation of spring cereal mixtures (SCMs) is one of the ways to increase the yield of crops in mountainous areas of Poland. There are only a few current long-term studies on this topic. Our study aimed at analyzing yield and competitiveness as well as the economic indicators of spring cereals in pure or mixed sowings in integrated or organic crop rotations over nine years. A field experiment including pure sowings of oats, spring barley, or spring triticale and their two-component SCMs, each in two systems, organic and integrated crop rotation, was carried out in the Mountainous Experimental Station in Czyrna, Poland, in the years 2011–2019. On average, cereals in the pure sowings and mixtures yielded 18% lower in the organic rotations compared with the integrated ones. However, SCMs yielded higher than the pure sowings, and displayed a higher leaf area index and land equivalent ratio. The average gross margin without subsidies was almost two times higher in the organic crop rotations than in the integrated ones, which was influenced mainly by the cultivation of barley in pure sowing. Summing up, the cultivation of SCMs in the mountainous areas of southern Poland is advised because of both productive and economic factors.

Solidago canadensis belongs to highly invasive species in Europe, it is established in ruderal, semi-natural and natural communities. To test the traits related to invasiveness, the experiment with the potential of allelopathic compounds produced by the species was conducted. The aqueous extract from the goldenrod leaves was used to examine the germination and early stages of development of Trifolium pratense, the species as an example of fodder plant common in meadows and pastures. Three types of aqueous extract were used: decoction, infusion, and macerate. All extracts of Canadian goldenrod had a negative influence on the germination process of red clover, however, the effect changed in time and type of extract. The most inhibiting influence was documented for the macerate type of aqueous extract. Similarly, the negative influence of macerate was the highest for the length and weight of the seedlings, the content of chlorophyll a and b, and electrolyte leakage. As the procedure of obtaining the macerate is the most like the process of natural extraction of allelopathic substances in nature, there is the practical conclusion to remove the moved biomass of the goldenrod during the restoration process of areas colonised by the species.

Solidago canadensis L. is an expansive perennial that forms persistent, species-poor plant communities. It often spreads in fallow areas, displacing native floristic ingredients. Its expansiveness is largely due to morphological features, but it can also be the effect of allelopathic interaction. The aim of the experiment was to investigate the effect of aqueous extracts (decoction, infusion, and maceration) from dry S. canadensis leaves on germination and early growth stages of Raphanus sativus L. var. radicula Pers., in three cultivars: ‘Rowa’, ‘Półdługa’, and ‘Krakowianka’. In comparison to the control, the percentage of germinated radish seeds of ‘Rowa’ cultivar was statistically lower on the infusion and macerate. Regardless of the cultivar, the smallest changes in germination were found in seeds watered with decoction, and the largest with macerate. Seedlings length was most inhibited on macerate substrates, and least with infusion. Regardless of the form of the extract, each of them negatively affected the initial growth of radish seedlings. A fresh mass of ‘Rowa’ seedlings was inhibited by all Canadian goldenrod extracts. In relation to the control, the ‘Krakowianka’ cultivar was the least sensitive to S. canadensis extracts. The total chlorophyll content was the lowest in the seedlings of the ‘Rowa’ and ‘Półdługa’ cultivars germinated on macerate, compared to the control and two others extracts. The percentage of electrolyte leakage depended on the type of extract used and the radish cultivar. The study showed that depending on the cultivar, the aqueous extracts from S. canadensis leaves decreasing of germination and early growth of R. sativus.