Don’t let its relatives mislead you. Garlic’s close cousin, the onion (Allium cepa), is more adaptable about its ideal moment to be lifted and cured. You can simply let the tops (leaves) die down right in place, delaying digging a bit to when it’s convenient. Or if you’re in a rush, move things along (assuming the bulbs are well-formed) by knocking over the foliage to urge the plants toward their finale.
With garlic, though, waiting until all the leaves go brown will promote overripe bulbs whose cloves are starting to separate from one another, and the resulting un-tight heads won’t store as long. Each leaf that browns is one fewer potential wrapper to protect the bulb. (Counterpoint: Harvesting too soon can also diminish the bulbs’ shelf life in storage, and may limit the bulbs reaching full size.)
Most experts say to harvest when several of the lower leaves go brown, but five or six up top are still green—and depending on the weather, this typically happens here in my Northeast garden in late July. Above, those are a few plants just as they came from the ground one year. Early bouts of sustained spring heat can push the garlic a little ahead of schedule (as with so many other plants), and have my harvest curing extra-early, a process that takes three to eight weeks, before the tops will be cut off, the roots trimmed, and the cured bulbs Read more on awaytogarden.com