do you cut them when you mow the grass? how old are they, as they take a few years to flower, do you feed them with a high potash food, (ie tomatoe food)

As above though they shouldn't really need feeding. I would guess that they are C. hederifolium which flower at the end of summer and that you have mown the buds off. In a flower bed they would grow to three or four inches tall, well above lawn grass level.