I have two rhododendron catawbiense that I planted in May 2011. That first year they bloomed lightly -- already blooming in the containers when I bought them. They seem to be healthy and have grown, but they didn't bloom this year. I used Hollytone this spring. I have not pruned them. Is there anything else I can do to help ensure they bloom next year? They get plenty of sun -- full sun all afternoon, which made me hesitant to plant them in this location, but I read this type can take a lot of sun. I am just wondering why they didn't bloom.