Spring for me too. My best time is March - April. We may get a cold, snow snap in that time but it does not last long and it is cool enough and enough rain to really get the plant going. I have lost everything I have planted in June or Fall.
Also, in my climate I was told by my local nursery to never plant Oriental Lilies and Asiatic Lilies in the Fall. Those are planted in the Spring.
June it gets to hot and dry and Fall we have too much rain that goes right to freeze then thaw, then freeze then thaw. Certain death for the plants.
