Green Alkanet (Pentaglottis sempervirens) is one of those rogue plants that insists on being prolific despite the efforts of many gardeners to treat it as a weed. It is brimming with blue forget-me-not flowers in spring and early summer and brimming with bees. I would suggest that it is one of the plants that is sustaining bee populations in urban areas by virtue of being an abundant wild flower. 
 It can spread rapidly by self-seeding and be difficult to eradicate because it has a deep tap root but it is certainly not uncontrollable. I am happy to see its spray of blue flowers and evergreen leaves here and there in the garden. I particularly enjoy the way it takes hold in neglected parts of the urban landscape to form large patches.
 "Alkanet" is a derivation from the Arabic word for henna (and is a common name for a number of dye plants in the Borage family). It is speculated that this species may have been introduced to Britain from south-west Europe to use the roots as a source of brown-red dye. I gather Alkanna tincturia is accorded the name True Alkanet for its superior properties in that regard.