Borage - Borago officinalis

Borage is one of the easiest and best bee plants that I have found.  It has many advantages for both gardeners and beekeepers:
For gardeners

Borage is a herb and the seed packet will tend to tell you that the cucumber leaves taste nice in a Pimms. This is true but greatly undervalues the plant;

grows very easily from seed – just push the big seeds into the soil and off they go
plants grow to about 2ft with masses for beautiful blue 5 petal flowers from May to October – employ the ‘Chelsea chop’ to some plants in June to keep them tidy and flowering well.
because bees love them they are great for attracting pollinators to your veg or soft fruit patch
they self seed so, as long as you avoid weeding them out, you will get a good crop free next year in either flowerbed or veg patch
For Beekeepers

Borage provides high levels of both nectar and pollen and flowers for 3 months or more providing:

food supply from late spring/early summer, through the June gap, into late summer
depending on how much is available, can produce a very high yield of honey
the honey is pale, runny, delicate and slow to set – may be able to off-set some of the fast setting effects of rape if both are present in the area
if planted around the hive as a forage boost, it will out-compete weeds if planted early.
Source http://www.rosybee.com/