Quantifying variation among garden plants in attractiveness to bees and other flower‐visiting insects

Abstract

Summary1. Pollinating insects are globally declining, with one of the main causes being the loss of flowers. With the value of countryside reducing, urban areas, particularly gardens, are increasingly recognized as of benefit to wildlife, including flower-visiting insects. 2. Many gardeners specifically select plant varieties attractive to wildlife. Given the wide public interest, many lists of recommended varieties have been produced by both amateurs and professional organizations, but appear not to be well grounded in empirical data. These lists, however, are not without merit and are an obvious starting point. There is clearly a need to put the process onto a firmer footing based more on data and less on opinion and general experience. 3. We collected data over two summers by counting flower-visiting insects as they foraged on 32 popular summer-flowering garden plant varieties in a specially planted experimental garden, with two smaller additional gardens set up in year two to check the generality of the results. With many thousands of plant varieties available to gardeners in the United Kingdom, and other countries or regions, it would have been an impossible task to make a comprehensive survey resulting in a complete and authoritative list. 4. Our results are valuable and encouraging. Garden flowers attractive to the human eye vary enormously, approximately 100-fold, in their attractiveness to insects. Insects, especially bees and hover flies, can be attracted in large numbers with clear differences in the distribution of types attracted by different varieties. 5. Our results clearly show that there is a great scope for making gardens and parks more beeand insect-friendly by plant selection. Horticulturally modified plant varieties created by plant breeding, including hybrids, are not necessarily less attractive to insects and in some cases are more attractive than their wild-type counterparts. Importantly, all the plants we compared were considered highly attractive to humans, given that they are widely sold as ornamental garden plants. 6. Helping insect pollinators in gardens does not involve extra cost or gardening effort, or loss of aesthetic attractiveness. Furthermore, the methods of quantifying insect-friendliness of plant varieties trialled in this study are relatively simple and can form the basis of further research, including 'citizen science'.

Insights from measuring pollen deposition: quantifying the pre-eminence of bees as flower visitors and effective pollinators

“…Firstly, the number of immediately preceding visits to the same species that a particular visitor has made will potentially affect the amount of pollen it then deposits on the virgin flower we sampled; but there is no intrinsic reason (other than sheer floral density) why this influence will vary markedly amongst the various plants studied here, other than that some hybrid garden plants may have modified pollen amounts or accessibility compared to the native species (e.g. Garbuzov and Ratnieks 2014). Secondly, SVD records may be directly correlated with floral density, especially for bees, since multiple quick visits may move a greater percentage of the pollen from the pollinator's body onto the next flower, whereas in sparsely Fig.…”

Plant diversity and composition compensate for negative effects of urbanization on foraging bumble bees

“…However, cities can also provide new (foraging) habitat for animals (Paker et al 2014), and some studies revealed gardens, parks, and meadows as islands for insects (Gaston et al 2005a;Matteson et al 2008;Ahrné et al 2009;Garbuzov et al 2013).…”

Ornamental Representatives of the Genus Centaurea L. as a Pollen Source for Bee Friendly Gardens

“…Forage flora consist of crop plants (Delaplane and Mayer, 2000) and wild species from natural and anthropogenically transformed communities (Wrzesień and Denisow, 2006;2007;Denisow, 2011). However, due to changes in crop structure and habitat loss or degradation, the value of countryside is decreasing but the value of urban areas, including ornamental gardens, is increasingly being recognized as an important source of food plants supporting a rich diversity of pollinators (Fussell and Corbet, 1992;Denisow and Bożek, 2006;Strzałkowska, 2006;Denisow, 2011;Garbuzov and Ratnieks, 2013). High flora diversity has been recorded among urban green spaces, such as parks, botanical gardens, private ornamental gardens, cemeteries, and railway areas; therefore, these areas are supportive to wild pollinators (Wrzesień and Denisow, 2006).…”

“…Because garden plants are often non-native, their usefulness for pollinator-friendly gardens requires observations of phenology, flowering biology and ecology, insect visitors, and the availability of floral reward (Denisow and Bożek, 2006;Strzałkowska, 2006;Masierowska, 2012;Denisow and Strzałkowska-Abramek, 2013). These studies are of great importance as the variation in the total number of insects attracted by ornamental species is broad (80-300-fold) (Garbuzov and Ratnieks, 2013). In Poland, the value of a floral reward from numerous ornamental herbaceous perennials, including species of the families Ranunculaceae, Saxifragaceae, and Malvaceae was highlighted by Denisow and Bożek (2006), Masierowska (2012), and Antoń and Denisow (2014).…”