Garlic bulbs are ready to harvest in late spring or summer, from seven to eight months after they are planted. The outward signs are the green leaves, which will begin to turn brown, and the flower stems – if present – which will begin to soften, although staying green. If you are not sure, just pull back the soil around one of your bulbs, if the clove ridges are clearly defined and the bulbs are a decent size, and some of the leaves have died back, then harvest them.
Don’t leave harvesting until the leaves die back completely as with onions, because by this time the bulbs will have started to split. Once the bulbs have split, they are still fine to eat, but won’t store for long. So eat these ones first.