Impact of Picking Time on Leaf Quality Parameters of Three Varieties of Honeysuckle ( Lonicera caerulea L.)

Lonicera caerulea is a nutrient-rich plant of significant importance. Its chemical composition is influenced by various intrinsic properties and external factors, which change with the seasons. This study aimed to evaluate the effects of different picking times on the proximate composition and the contents of pigments, macroelements, bioactive compounds and antioxidant activity in honeysuckle leaves. Seasonal changes in the contents of fiber, ash, proteins, nitrogen (N), potassium (K), magnesium (Mg), phosphorus (P), calcium (Ca), chlorophylls, total carotenoids, total flavonoids and total phenolics were analyzed. The results revealed that picking time and plant variety significantly affected the chemical composition of honeysuckle leaves. The first picking yielded the highest levels of protein, N, P, K, chlorophyll a and b, total chlorophyll and total carotenoids. Conversely, the third picking showed the highest levels of Ca and Mg. Specifically, the third picking of ‘Indigo Yum’ leaves had the highest Ca and Mg contents, while the second picking of ‘Zojka’ leaves (116.67 mg 100 g −1 DM) and the third picking of ‘Wojtek’ leaves (115 mg 100 g −1 DM) contained the most total flavonoids. The first picking of ‘Wojtek’ leaves recorded the highest levels of protein, N, P and total carotenoids, whereas the third picking showed the highest fiber and ash contents. These findings provide valuable insights for farmers, enabling them to select appropriate cultivars and optimal picking times to produce high-quality honeysuckle leaves for use as food or medicinal supplements.