From late September until the middle of November is pretty much the window of time I use to plant my garlic which are planted at all different times, each batch a couple weeks apart, and altogether, there are nearly 1000 cloves planted. The spacing is also variable. I have some of the only 3-4 inches apart, some around 6 inches apart while today, I just created a huge garden bed not in any of these pictures with garlic spaced around 1foot apart to see how much bigger they get with the extra space. It is necessary to plant them in the fall as opposed to the spring for maximum sized bulbs because it gives them an extra half a year to produce roots, growth hormones over their dormancy period, and come out strong once the snow melts.
These in the closest bed are spaced close to 6 inches apart which is a pretty good benchmark for decent sized bulbs. Closer planting generally results in higher overall production as long as there is very rich soil while wide spacing will usually result in larger bulbs so I mix it up.
Here's a closeup of the tallest bed so far. These are probably around 6 inches tall and should have another 2-3 inches of growth left through december as long as the soil is not frozen yet. I have found that as long as they are planted and are 1-10 inches tall by the end of autumn, they are planted at the right time because they will have a root system developed, the cloves will turn into rounds, and even over winter when they are covered by several feet of snow, I believe that root growth resumes through the winter as they generally come up much larger the following spring.
Others are more like 2 inches tall and depending on how much precipitation we get as well as the soil temperature, I expect this batch to end up around 5 inches tall going into winter.
Here are some more garlic from scapes produced in 2010 which are now around the same size as the ones from cloves so they should form full bulbs by next spring.
Here's a pot of onions and scallions, a closely related plant to the garlic, and these are pretty much the only plants show active growth from october through december.
Here's the elephant garlic. These don't really have as much flavor as the smaller types so I only plan on planting a few just for show.