Geraniums are not often top of the lists of plants for bees but I think they are under-rated. Geraniums are a real stalwart of any herbaceous border. The extensive range starts blooming in April with the Phaeums and keeps going right through to August with the Oxonianums which repeat flower for a very long time. But, as with all garden plants, they come from the wild and in the UK we have two very common native geraniums:
1. Pratense (bloody cransbill) - a tall willowing blue flowered plant that you commonly see with its head above the grass flowers at the edges fo the road and
2. pyrenaicum - a low growing, creeping variety with masses or small purple flowers
Both flower from end of May till end of June and hence provide a regular reliable source of 'June gap' nectar and pollen.
All the geraniums (with the exception of a few cultivated doubles) have an open flower which is perfect for all types of bee.
If they are planted in a big clump then you will see a variety of bees on them. Thier flowers are not packed closely together and so honey bees might find them an inefficient source if its only a single plant if there is competition nearby. However, if other flowers are scare in June then the reliable geraniums will be most welcome.