Thank you for your timely question, Annamarie!

First:  it IS time to plan your garlic!  You'll find advice ranging from two - six weeks before the first frost in your area and we are close to experiencing a frost here in northern Vermont.

The more challenging part of your question is the "elevated -- off the ground" bed.  You didn't mention the dimensions, so I'm envisioning an elevated bed that's not terribly large....perhaps 4-8' long and no more than 3' wide.    

You're correct that raised beds are often recommended for growing garlic because the bulbs need to be in well-drained soil and your elevated bed offers this advantage.  I grow garlic in a raised bed that's just six-ten inches above my clay soil;  the garlic's so happy in my amended soil that it's almost invasive.  In an elevated bed, though, the soil will probably freeze sooner....it's OK that the soil freezes, but the bulbs you plant need time to send out roots.  You might also see the garlic sprouting prematurely if your elevated bed sits in a very sunny spot and we have mid--winter thaws.

If you are willing to experiment (this is how I first approached raising garlic):  I'd recommend buying one head each of different types of hardneck garlic (does better in cold climates than softneck) to test.  Be sure to buy from a good garden center -- don't use garlic from a grocery store (this garlic is often treated chemically to avoid sprouting and may not even be a good type to grow in Vermont).  I'd label the planted bulbs clearly and I'd also probably try not to plant the bulbs right up next to the outer walls of the container (where the soil will freeze sooner). If your container soil needs any amending, take care of that before you plant -- this is a great time to add compost.  Yes:  definitely add a good layer of mulch.  Straw is ideal (not hay....which contains seeds), but fully dried leaves or grass clippings can be used, too. 

Here are three good fact sheets you might consult before planting:

• From the University of Minnesota (similar climate zones to ours):  https://extension.umn.edu/yard-and-garden-news/last-chance-plant-garlic
• From Rutgers (contains a good chart of garlic types to consider):  https://njaes.rutgers.edu/fs1233/
• From the University of Maine (contains helpful video clips): https://extension.umaine.edu/publications/2063e/

Finally: in case you haven't already thought this through:  the garlic will need to stay in your elevated bed until you harvest it in June/July.  Do you normally want to plant flowers or other vegetables in that space in the spring?  

I hope this helps and if you decide to experiment:  I hope you are rewarded with a bumper crop of garlic!  

-- Robilee Smith