Fall is the ideal time to plant garlic.
Garlic can be planted anytime after the first fall frost. Check your area’s first fall frost date and adjust accordingly.
However, just because the first frost happens, doesn’t mean that the weather is going to stay cold! A week or two of unusually high temperatures can signal garlic that its time to start growing–which you definitely don’t want. It can be a bit tricky to find that magic window of cold weather-but-the-ground-isn’t-frozen.
Gardeners will have success planting garlic anywhere from early September to late October. Most gardeners seem to favour planting anytime from October 1st-15th. If you’re from another area, try to plant your garlic 2-4 weeks after the first frost date.
Garlic should be planted 3-4 inches deep, 5-6 inches apart. A deep snow cover is important, and if there is concern this may not occur you can mulch with leaves in the fall and shovel snow over the planting sight to create a "blanket".