Posted by Dr G. Bittar
A thorough and most informative research performed in England, where the attractiveness and usefullness to pollinators of garden flowering plants was investigated.
Most attentive and imaginative gardeners, artists of landscaping, will be vindicated with a comment from Prof. Ratnieks, which goes opposite to the current myth that pollinators have no use of non-native plants: “Garden plants do not have to be native to help most pollinating insects.” (in “Flower research shows gardens can be a feast for the eyes – and the bees“)
The complete research article can be found on
http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12178/full
Here’s the summary and the introduction.
Dr Gabriel Bittar
Quantifying variation among garden plants in attractiveness to bees and other flower-visiting insects
Mihail Garbuzov and Francis L. W. Ratnieks
Functional Ecology, October 2013
Article first published online: 17 OCT 2013
DOI: 10.1111/1365-2435.12178
Summary
1. 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 bee- and 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’.
Introduction
Global biodiversity is in decline (Barnosky et al. 2011). Pollinating insects are no exception, with the main factor being loss of flowers, driven primarily by human activities, such as development and agricultural intensification, which lead to habitat loss and degradation (Goulson et al. 2005; Biesmeijer et al. 2006; Potts et al. 2010). With the wildlife value of the countryside reducing, the value of urban areas is increasingly being recognized (Frankie & Ehler 1978; Cane 2005; Dearborn & Kark 2010; Sanderson & Huron 2011). High species diversity has been recorded in urban green spaces, such as parks and gardens (Helden & Leather 2004; Matteson, Ascher & Langellotto 2008; Owen 2010), with private gardens often being the largest and probably the most important component (Goddard, Dougill & Benton 2010). In the United Kingdom, 87% of households are associated with a garden (Davies et al. 2009) and gardening is a popular hobby (Taylor 2002). In addition, many gardeners are supportive of wildlife, with most UK gardeners (74–78%) engaging in some form of ‘wildlife gardening’. That is, doing something to attract or encourage wildlife (Good 2000), including the 31% who select plants attractive to wildlife or the 66% who feed birds in their garden (Mew et al. 2003; DEFRA 2007).
Garden plants are often non-native, and this may reduce their usefulness to some wildlife. For example, many herbivorous insects have a narrow range of suitable food plants (Novotny & Basset 2005; Dyer et al. 2007). However, this does not prevent them from being useful to flower-visiting insects seeking nectar and pollen, as these are general resources. Nectar, for example, is mainly sugar and water (Nicolson & Thornburg 2007), and so it is edible whether from a native or a non-native plant. Many garden plants have also been bred to alter their appearance, such as by the ‘doubling’ of petals, which may reduce floral rewards or their accessibility (Comba et al. 1999; Corbet et al. 2001).
Given the public interest in helping wildlife, a large number of recommended plant lists have been produced, by both amateurs (e.g. Baines (2000); Lavelle & Lavelle (2007)) and professional organizations (e.g. Royal Horticultural Society (2011); Xerces Society (2011)). However, these appear not to be well grounded in empirical data. For example, Thompson (2006) referred to one list of wildlife friendly plants produced by Natural England, a government-funded agency responsible for protection and improvement of the natural environment, as ‘looks very much as if it was put together late one Friday afternoon’. In addition, lists of bee- and butterfly-friendly plants vary greatly even when they are for the same country, suggesting that the underlying information is based mainly on personal observations, experience, opinion and, perhaps, uncritical recycling of earlier lists (M. Garbuzov & F.L.W. Ratnieks, unpublished data).
Lists of bee- and butterfly-friendly plants are not without merit and are an obvious starting point for determining which plants are good for flower-visiting insects. However, there is a need to put the process onto a firmer footing based more on data and less on opinion and general experience. This study is an attempt to do this. We collected data over two summers in which flower-visiting insects were counted as they foraged on 32 popular garden plant varieties in a specially planted experimental garden. In addition, two smaller gardens were 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, it would have been an impossible task to make a comprehensive survey resulting in a complete and authoritative list. What our data do show, however, is valuable and encouraging. Garden flowers attractive to the human eye vary enormously, approximately 100-fold, in their attractiveness to insects. This shows that plant selection can make a great difference in the value of gardens and parks to flower-visiting insects, and at no additional cost. Insects, and especially bees, can be attracted in large numbers with clear differences in the distribution of types attracted by different garden plant varieties.
See also
An invasive daisy can be favourable to local pollinators — Prasad and Hodge 2013