They certainly work the wild 'dog' roses here in the UK - these have single 
flowers - and solitary bees also work them.

We are less likely to see bees on the cultivated roses, probably because 
they cannot get to the centre of the flower until it has opened fully (by 
which time many gardeners will have removed it).

Best wishes

Peter Edwards
[log in to unmask]
www.stratford-upon-avon.freeserve.co.uk/

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