Your garlic will be fine. My cloves always sprout. The greens will hang on all winter and will even grow some during warm spells. The tips of their leaves might get a little frost damage though but it's nothing to worry about.

And you planted at the right time (fall). If you plant in spring the bulb size will be smaller. They grow best when they are overwintered.

Rodney

I usually plant around now and they usually sprout between November and December.

Fall is the best planting time in our zone. I usually wait until we get our first frost before I plant my garlic bulbs. Some years, the garlic will start to sprout before growth stops, some years you won't see growth until spring. Either way it doesn't affect the plants, and in the spring you'll get lots of growth and nice big bulbs to harvest in the summer.

Garlics are frost hardy. In GA, I used to plant them in October and they would grow about 4" tall before frost. The winter lows sometimes dropped to mid teens but it won't bother garlics. But Up North, it can get down to ZERO and lower, Then maybe you wouldn't want you garlics to sprout in the fall. If they do sprout then you have to mulch them real heavy. Not to protect from cold but prevent temperature swing in the soil.

My garlics: Feb. 10, 2010.

I have never mulched my garlic in the past. However, I did this year using some ornamental grasses, because I had to plant them now, rather than November. I will be away during my typical planting time. I'll see how that goes. Even planting in November, I still get some top growth, it seems to have no big change in the size or quality.

Jim

I plant my garlic in the fall and sometimes they do come up by November if the temperatures remain mild. To me this not a problem, but as i am in Norway and temp can get to 0F, i always put a layer of straw on the top of the bed to act as an insulator for over winter.
Ralph

You don't have to mulch them. I've left garlic plants in the garden for two winters and the plants are fine. I do this because from one clove, you get 6 new bulbs...each clove in the first summer's bulb makes a whole bulb the following year. They're very hardy.