Abstract <p><i>Myricaria bracteata</i> Royle and <i>Myricaria longifolia</i> (Willd.) Ehrenb. (Tamaricaceae) are used as herbal medicines in Mongolia, China, and Russia (Siberia). <i>M. bracteata</i> has been domesticated and is used in landscaping thanks to its high winter hardiness, drought resistance, and decorative properties. <i>M. bracteata</i> and <i>M. longifolia</i> leaves are reported to contain derivatives of 17 flavonoid aglycones, as well as ellagic acid and its derivatives. A principal component analysis of 10 populations of each of these species, based on 56 parameters of the phenolic composition of twigs, has shown a high similarity between the species. The native populations of <i>M. bracteata</i> from Tajikistan and Khakassia, as well as native and cultivated populations of both species from Altai Republic, exhibit the most significant differences from most samples in the composition of the analyzed components. Populations of <i>M. longifolia</i> of Altai origin are distinguished by the maximum content of the sum of phenolic compounds (up to 107.7 mg per 1 g of dry weight), hyperoside (18.1 mg/g), and quercitrin (2.8 mg/g). The composition of the exudative compounds of the twigs of these species is also characterized by a high similarity. Differences in the concentrations of compounds by year are revealed. The exudates exhibit higher antioxidant activity (IC₅₀ 34.2 and 42.2 μg/mL) when compared to the extracts (IC₅₀&#xa0;110.7 and 172.2 μg/mL). Histochemical visualization shows the localization of phenolic compounds in the salt glands, vascular tissue, and chlorenchyma in leaves and stems. The results uncover the high potential of native and cultured plants of the Siberian <i>Myricaria</i> species as sources of pharmacologically valuable compounds, in particular, in the phyllosphere of plants, which allows us to consider these species to be elements of natural air purification and a way to improve environmental air quality parameters.</p>