Re: Growing garlic in raised beds?
I (Margaret) grow mine in raised beds here in Zone 5, where I can get to similar temps as you can (and do).
My beds are maybe 8 inches above ground (they are taller, like 10 inches of wood, but not brimming with soil).
I would highly recommend choosing a HARDNECK variety as your basic crop, since hardnecks (which will also give you the benefit in May or June or garlic scapes to cut off and eat) have deeper root systems and will anchor themselves better in our heave-and-thaw worlds. The details can all be found from here: