Posted: 23/01/2015 at 22:50
Shrinking Violet is right, annuals sell well, but it depends on when the sale is. I do plant sales for charity though and I can usually choose when.
When I divide perennials in autumn and spring I pot some up and keep them in a cold frame, no lid, unless they are a bit tender. So I include perennials but have more annuals. For the annuals I Google the pictures and put them on Word pages which I print and put out so people can see what they will grow into. Most people who buy aren't knowledgeable gardeners. Ask friends and parents too, nothing venture, nothing gain!
Last year I sowed too many petunias. I found a load of large flower pots in a skip so I planted pots with 3 or more petunias and they sold well. If you have time you can paint or decorate the pots, or the schoolchildren can.