Professor Dave Goulson, a conservation biologist at Stirling University's Bumblebee Conservation Trust (BCT), claimed "suburban gardens" full of "bedding plants from B&Q" and garden centres are such poor sources of pollen and nectar that they might as well be full of plastic blooms.
He added: "A lot of annual bedding plants that are widely sold from garden centres are of very little interest to insects or any other wildlife because they are bred selectively to be large and showy, and that results in plants with little pollen that insects can't get to. You can have a garden full of flowers that attracts hardly any insects.
"It would be nice when plant breeders are selecting marketable traits that they bear in mind that flowers originally evolved to feed insects and get plants pollinated. Many have lost that function."
But Sussex University professor of apiculture Francis Ratnieks, who is comparing summer blooming garden plants in terms of the number of insects that visit them to evaluate garden plants, said Goulson's position was "simplistic".
"Some bedding plants can be very good and others are not visited at all. I do not agree that bedding plants from B&Q are poor sources of pollen and nectar and might as well be plastic. This is far too simplistic. Some bedding plants are good and some cottage flowers will be poor. I would recommend that people look at bedding plants before they buy them to see whether they are being visited by insects, including bees."
NFU chief horticulture adviser Dr Chris Hartfield said: "Bedding growers are selling plants that the market demands. The bedding market has not specified that it wants plants that are good for bees yet."
British Protected Ornamentals Association (BPOA) treasurer Simon Davenport said: "Gardens serve many purposes as well as benefiting wildlife. BPOA members are interested in furthering biodiversity in gardens in a variety of ways. Gardeners who plant bedding will also be planting herbs, shrubs and trees in a good garden design, which provides a habitat of benefit to bees and other insect pollinators.
"Moreover, there are a number of plants used in bedding and hanging basket displays that are good for bees in terms of nectar and pollen. There is the very important Impatiens and Lobelia, as well as Alyssum, Arabis, Aubrieta, Cheiranthus, Dahlia, Fuchsia, Hedera, Lamium, Salvia and Viola. Summer flowering bedding can also attract bees when there is a gap in pollen and nectar sources after spring."
Goulson said the BCT had been working with Garden Centre Group to encourage people to grow more cottage garden flowers, "which are closer to their natural form and tend to be more useful to bees and butterflies". He recommended lupins, lavender, foxglove, chives, thyme, sage, aquilegia, marjoram, comfrey and catmint in particular.
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