Mix one bushel of peat moss, potting soil and perlite to make a lightweight potting medium for container gardens. Add 1 to 1 1/2 cups of 10-10-10 fertilizer and mix it in well with the potting mixture. Because garlic prefers slightly acidic soil -- pH between 6.2 to 7.0 -- lime typically is not needed.
Fill the pots to within 1 inch of the rim with the potting mixture. This allows room for watering.
Separate the head of garlic into individual cloves. Plant the garlic cloves with the pointed end up to a depth of 1/2 to 1 inch. Space cloves 4 inches apart to allow room for the bulbs to form. A 12-inch pot can hold 4 or 5 garlic cloves.
Cover the cloves with soil and push them down to secure the cloves in the soil and remove air pockets. Water thoroughly until water runs freely through the bottom of the pot. Place the pot in a sunny location. Water when the soil feels dry to the touch 1 inch below the surface.
Keep the pot in a cool location, outside is preferred, until spring. Cover with a layer of hay or leaves to prevent heaving from freezing and thawing.
Apply water soluble fertilizer designed for vegetables on a 7- to 14-day cycle. Plants grown in containers often require more frequent applications of fertilizer than those grown in the garden, as nutrients leach from the soil with watering.
Harvest garlic in the fall once foliage has died off and bulbs have formed.