wallflowers and sweetwilliams are they left in the ground cut back or pulled out after flowering

I think it was yesterday someone asked this question about wallflowers and was told to pull them out. They are part of the same family as brassicas, i.e. cruciferae, and can get club root and infect your veggies; also as they are bi-annuals they are unlikely to flower again. Sweet Williams are annuals so they also can be pulled up once flowering is over.

I leave my sweet williams in the ground after they have flowered the first year. The plants spread well and flower the following year. I also collect seed, so always have some plants. The flowers are good for cutting and last well indoors.

Pasuki it is the seeds that grow up to be next years flowers

Sorry to disagree Moongrower but I've had plants that have definitely survived and flowered for two or even three years, before they've grown straggly and have been replaced.

Guess that will be one of the differences living in Essex - certainly would not survive here.