Ключевые слова: allergic, allergy, asthma, background, bark, beautiful, betula, betula pendula, betulaceae, birch, birch pollen, bloom, blooming, blossom, botanical, botany, branch, bud, catkin, catkins, environment, flora, flower, flowers, foliage, fresh, garden, green, growth, health, inflorescence, leaf, leaves, medicinal herbs, natural, nature, outdoors, park, pendula, plant, pollen, season, seasonal, spring, springtime, tree, tree bark, twig, wood bark, young,