Some bumblebee species Bombus spp., particularly long-tongued species, have undergone substantial range contractions in the UK and may be suffering from a lack of nectar and pollen supply in the wider countryside. This study tested the use of different types of garden-planted Cotoneaster (Rosaceae) by bumblebees from May to August, in the Cambridge University Botanic Garden, Cambridge, England.
Twenty-four different species and forms of Cotoneaster are planted at the University Botanic Garden, Cambridge, with one or a few bushes of each. The genus is in two sections – the Cotoneaster section, with cup or bell-shaped flowers, and the Chaenopetalum section, with open, saucer-shaped flowers.
The number of bees visiting one bush of each type of Cotoneaster was recorded on a single standardised walk, taken between 12:00 h and 17:00 h, on 21 days between 17 May and 19 August 1988 when the ambient temperature was 16-28°C. Flower abundance was scored for each Cotoneaster type.
At least one type of Cotoneaster was flowering at any one time from the start of the study until the second week of August.
Short-tongued bumblebees of the species group B. terrestris/lucorum (white-tailed and buff-tailed), and honey bees Apis mellifera visited Cotoneaster plants in both sections of the genus. Plants of the section Cotoneaster were visited more by these bees in May and early June, a critical period when other forage may be scarce.
The common carder bee B. pascuorum and the early bumblebee B. pratorum almost exclusively visited plants in the section Cotoneaster throughout the season.
The study shows that a mixture of Cotoneaster species can provide a seasonal succession of forage for bumblebees and honey bees from May to August. The paper lists 24 varieties of Cotoneaster, with information about their peak flowering time and resistance to fire blight (a bacterial disease that can be transmitted to some fruit trees by bees).
If using or referring to this published study, please read and quote the original paper, which is available through the International Bee Research Association http://www.ibra.org.uk