How cool does it need to be to start mailing plants for plant exchanges? On tree and shrub seedlings do you wait until they're dormant or just until the weather cools off?
I usually start mailing plant exchanges in Sept. when the days are about 80 or less. As for trees it depends on the type. Hope this helps.
christie, I just received a box of live plants that took 4 days to arrive and they were in great shape, not even wilted, so I guess now is good! Of course they were from a colder area to a warmer.