For the last two weeks (end March - early April) I have been observing the bees on a large flowering currant in my back garden mainly because, other than the daffodils, its one of the biggest sources of flower right now. It is 2 meters high and completely draped in pink blossom; quite the most magnificent display I can remember since we moved into the house 12 years ago.
Initially I was surprised at how few bees were being attracted; just the odd queen bumblebee or honey bee every few minutes, really very few for the amount of flower. Then one evening I happened to be weeding under the bush and became aware of an increased level of buzzing from above. As I stood up I was assailed with a strong perfume which i realised was coming from the bush. I had not noticed any perfume during the day so I concluded the flowering current is evening-scented and the result, of course, was that the bee numbers increased significantly.
That evening, at any one time there were 5 or 6 bumblebees and several solitary bees foraging. It was 6 o-clock so maybe a bit late for honey bees.
I cannot find anything documented about Ribes being evening-scented but that is definitely my observation. Interestingly I dont think it is night-scented which is a trait of plants that aim to attract night-flying insects and notably moths. Therefore it is this plant is aiming to attract bees that are still flying on a nice warm spring evening. Its amazing how they all manage to find their niche to compete and survive.