Sorry Suzanne, I always assume that most gardeners are familiar with common hanging basket plants. Of course, on here, I should realise that most members grow vegetables. Bidens are often included in those huge baskets the local councils do to hang in town centres and shopping areas.
I have all the seeds I need for this years baskets and tubs but wanted to add Bidens this year. The only edible things I grow are tomatoes, chillis, peppers and some lettuce. Looks like I will have to buy some. I did look in Wilkinsons but they didn't have them this year.