A bag of garlic looks like groceries, but biologically, you’re also looking at a surprising amount of potential planting material. Each bulb separates into individual cloves, and each healthy clove can potentially grow into an entirely new bulb, making planting garlic in fall one of the more satisfying ways to turn a small amount of planting stock into a much larger harvest. The math is simple: one planted clove can produce one head of garlic. If your $5 purchase contains several bulbs with multiple large cloves apiece, it’s easy to see how the multiplication works. There is one important catch, however: the cheapest supermarket bag isn’t necessarily the garlic you should put in your garden.