Abstract
Summary Urban areas have a specific ecological environment and may help to sustain local pollinator populations by the cultivation of different ornamental plants with entomophilous flowers. This yearlong study examined the flowering pattern, abundance of flowering, pollen production as well as insect visitation of two cultivars of the ornamental shrub Potentilla fruticosa L. (‘Maanleys’ and ‘Blink’), grown in Lublin; a city in south-eastern Poland. P. fruticosa ‘Maanleys’ bloomed from the middle of May to the first decade of September and P. fruticosa ‘Blink’ from June until October. The pattern of diurnal flowering was similar for both cultivars and showed plasticity in the season. Flowers opened most intensively in the morning hours, and 80 - 90% of the daily installment of newly opened flowers expanded by 8.00 h GMT +2h. A delay in the peak of diurnal flowering was noted between the spring/summer and summer/autumn periods. The most intense blooming fell in the 2nd month of flowering. The mass of pollen produced per flower depended on both the number of anthers and the efficiency of archesporial tissues. The pollen output varied from 1.4 to 7.2 mg per 10 flowers (‘Maanleys’) and from 2.6 to 4.5 mg per 10 flowers (‘Blink’). The mass of pollen produced per individual shrub was substantially related to the abundance of blooming. The average estimated pollen productivity in the full flowering phase was low; 1 g (‘Maanleys’) and 1.5 g (‘Blink’) per 10 m2 of shrub crown. The flowers of Potentilla fruticosa attracted numerous insects, mainly solitary bees (33 - 43%), dipterans (31 - 42%), lepidopterans (4 - 14%), bumblebees (3 - 15%), and honey bees (3 - 4%). The Potentilla fruticosa ‘Maanleys’ and ‘Blink’ are propagated for specific ornamental arrangements and due to a long flowering period may be used in small urban courtyards for both decorative value and as a pollen delivering plants.
Highlights
Bees and other insect flower visitors need a continuous food supply throughout their whole life cycle
Until the early 1990s, agricultural areas received the most interest when it came to bee pasture improvement, while urban areas have a great potential for pollinator recovery (Fussell and Corbet, 1992; Masierowska, 2012)
The flowering began in mid-May (‘Maanleys’) or in June/July (‘Blink’) and lasted till mid-August or mid-September (‘Maanleys’) and till October (‘Blink’)
Summary
Bees and other insect flower visitors need a continuous food supply throughout their whole life cycle. Pollen and nectar provide the complete diet for both the adults and their larvae. All kinds of bees are threatened, mainly because their nesting sites and food plants are frequently destroyed by human activity (Williams et al, 1991; Torchio, 1994; Banaszak, 1995). This has resulted in a decrease in bee populations in many parts of the world (e.g. Goulson et al, 2008). Different ornamentals, i.e. shrubs, have been reported as a source of nectar and pollen flow (Szklanowska, 1983; Szklanowska and Strzałkowska, 2001; Kołtowski, 2006; Lipiński, 2010; Wróblewska and Stawiarz, 2012)
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