Perennial flowers are usually sold as plants which you can buy from a garden center. When you are purchasing one or two for a particular purpose it makes sense to buy an established plant. However if you are starting a new bed and need a large number of flowers the cost quickly mounts up and you should consider growing from seed. I found an article by Stephanie Rose on her Garden Therapy website in which she explains her approach and lists her choice of fourteen easy perennials to start from seed.
You can read her article at Garden Therapy
