|Bees love phacelia but it is really grown as a green manure plant.|
A useful plant in the fruit and vegetable plot is the green maure plant phacelia, although you are meant to dig it in to the ground before it flowers.
I do leave a patch of phacelia to flower as the bees love it, even if it self seeds it is not difficult to pull the plant out if it grows in places you do not want it too, just wear gloves as it is 'prickly' to touch.
I think the reason you dig phacelia in before it flowers is that it becomes more fibrous as it matures as well as the concerns about it self seeding into unwanted areas.
What is a green manure plant? A green manure plant is sown on a patch of the garden when no other crop is growing in that area, it helps to reduce the number of weeds germinating and at some stage it is dug into the soil to improve the condition of it. Green manure crops can improve the humus of the soil, so it helps with future moisture retention etc. It can make the soil easier to work if it improves it.