I purchased a melianthus major in late summer, and it is still in the pot. Would it be better to get it in the ground for the winter? What is the best way to overwinter this shrub? I don't have a greenhouse.
Probably can't pull off overwintering it in the ground-unless you're in a particularily sunny, well-drained spot. Some people get away with cutting it back and applying a heavy mulch, but I always lose mine to rot with this technique. Best bet would be keep the pot in a sheltered area (ie. put it up against a window under an eave), or inside in a cooler part of the house, not let it dry out, and put it back out in the late spring. That's worked for me: others might have more to add.
Best bet would be to plunge pot into mulch pile, rather than leave it sitting out in the air, to freeze up like a brick.