[FarmerShawn]

I'm no expert, but I think I have read that hard-necked garlic varieties do better in the north, where summer days are long, while soft-necked varieties do better in the south, where day length is more even. And I'm pretty sure the issue is day length, not heat. I'm also pretty sure that it's a generalization with exceptions, as I have a neighbor in northern New Hampshire that grows both kinds quite successfully.