There's an old wives' tale that garlic must be planted on the last full moon in October to be successful. While maybe not completely true, that is not a bad way to judge - anytime in October after the soil starts cooling off is close enough! This will give it time to start growing nice big heads for next year.

 

Plant individual cloves in well drained soil, 2 to 3 inches deep and 4 inches apart. Harvest next July when leaves go yellow and flop over.