FLOWERING AND NECTAR SECRETION IN TWO FORMS OF THE MOLDAVIAN DRAGONHEAD (DRACOCEPHALUM MOLDAVICA L.) - A PLANT WITH EXTRAORDINARY APICULTURAL POTENTIAL

Dracocephalum moldavica is a valuable reward plant for flower visitors. The aim of the study was to ecologically characterise its flowers and leaves and assess the seasonal and daily dynamics of flowering in two white- and blue-flowered forms of this species in 2004 and 2005. Additionally, the duration and abundance of plant flowering as well as the nectar amount and sugar content were analysed. The signalling attractants of the plant include an intense scent emitted by trichomes located not only on its flowers but also on its stem and leaf surfaces. The average corolla length is 24 mm and the corolla tube, which can be completely filled with nectar, is 8.6 mm long. The floral lifespan was shown to reach 2-3 days and the mean blooming duration of both forms of dragonhead 45-48 days. The white-flowered plants produced a substantially greater number of flowers (5352) than the blue-flowered form (2965). The nectar amount obtained from ten blue flowers was 15.33 mg and that extracted from white flowers reached 17.56 mg, with 49.4% and 51.5% content of sugar, respectively. The total sugar mass produced by one white-flowered plant was 4656 mg, while one blue-flowered plant yielded 2164 mg of sugars. The sugar yield calculated in the study for the white-flowered form (586 kg. ha(-1)) was two-fold higher than that in the blue-flowered plants.