I've been buying most of my annuals, veggie and perennials from Walkers for over ten years. They are wonderful. They have a huge selection and are most helpful when I have a question.
They also maintain their plants throughout the growing season - big box stores tend to let the plants dry out and then water them after the roots have been damaged or killed.
I love the fact that they are a family owned and operated business.
I highly recommend them!