The biological value of fresh and dried spice material is strongly influenced by climatic and agronomic conditions as well as by genetic and ontogenetic factors. In the available scientific literature, few publications present the problems of growing herbal plants for direct consumption and discuss the biological value of fresh herbal material. Therefore, the aim of the present study was to evaluate the yield and quality of tarragon herb grown for bunching depending on plant density (20 × 20 cm and 30 × 30 cm) and harvest date (beginning of July and beginning of September). This study was conducted during the period 2010–2012 at the Experimental Station of the Department of Vegetable Crops and Medicinal Plants, University of Life Sciences in Lublin, in south-east region of Poland (51º14’N 22º34’E). In fresh plant material, the contents of L-ascorbic acid, chlorophyll, carotenoids and essential oil were determined, while the contents of essential oil, tannins and flavonoids were determined in leaf herbage. The yield of tarragon herb grown for bunching was dependent on the plant density and harvest date as well as their interaction. Plants grown at lower density and harvested during the early summer period were characterized by better yield parameters compared to the other treatments. Tarragon herb harvested at the beginning of July was characterized by higher concentrations of L-ascorbic acid, chlorophyll a, b and a + b, flavonoids and essential oil as well as a lower content of tannins than the plant material harvested at the beginning of September. The carotenoid content in tarragon herb was not dependent on the factors studied, with their significant interaction. In growing tarragon for bunching, lower plant density can be recommended, since it contributes to high herb and essential oil yields. The beginning of July proved to be a more favourable time for harvesting tarragon grown for bunching than the beginning of September due to the quantity and biological value of tarragon yield and essential oil yield.

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