Posted: 01/06/2015 at 20:31
Sounds like you have the biennual ones which will set seed after they flower. I sometimes dead head for extra flowers. Leave the seed pods til they are brown and then resow.
I have the perennial type Bowles Mauve, the leaves are slightly different in shape and colour and it has a distinctive stem of purple flowers. Really lovely plant, can get quite big and shrubby if you trim off the flowers stems. It also flowers all year round and you can easily take cuttings