I’m in eastern Michigan and I am ordering from southern North Carolina. Our average first frost date is somewhere around October 15. I’m ordering two different varieties of Japanese maples. Sorry, should have put more information in the original post! I’m new to the bonsai forum world
You only have about 2 to 3 weeks of growing season left. In North Carolina, they probably have 6 to 10 weeks left depending on where they were. My friend just south of Charlotte NC, had a number of palm trees in her yard. Now they were "hardy palms" but it gives you an idea how much more mild NC climate is than Michigan.
The reason for my concern, is it takes months of progressively colder night time temperatures to trigger the metabolic changes needed for a maple to become cold hardy. Suddenly exposing a rapidly growing maple to a frost will damage tissue.
If I were you, when you get your maples, keep them outside. For 4 weeks leave them out, but if it is going to freeze at night, put them in the shed or garage or somewhere that stays just barely above freezing. You could even put them in a refrigerator which will chill them to 40 F (4 C) but won't frost them, to keep them progressing toward becoming freeze hardy.
Then after about 3 or 4 weeks, you can allow the maples to get light frosts. Shelter them if it will be colder than 25 F. (-4 C) After 8 weeks you can treat them like the rest of your bonsai. Shelter for the remainder of the winter the way you would normally treat your trees. ,
Key is, when moving them around to avoid a hard freeze, don't expose them to warmth, or you will undo some of the conditioning to adapt to cold. Warm would be anything over 45 F. for the night.
Sounds complicated, but sometimes the weather cooperates, we get a frost or two early, then might go a couple weeks before we get enough cold to freeze the ground. If you are lucky, you will only have to bring them in a few nights.
