A reliable harvest indicator is when half the leaves have died off, and half are still green. The leaves start to die off from the bottom up.
When at least 50 to 75 percent of your crop has reached the telltale stage of maturity—half the leaves are brown and half are green—stop watering your garlic for one week.
Lightly dig into the soil around a random bulb, or a few random bulbs (taking care not to damage any of the wrappers or cloves), and check its size without digging the whole thing up.
If the bulb looks small, pat the soil back down and wait a few more days before you check again. If the bulb looks substantial, the wrappers tight, and the cloves plump and well-formed, it’s ready to be harvested.
Carefully loosen the soil around your bulbs with a trowel and gently pull the garlic out from the base of its stem, at its neck. Brush off any excess dirt that falls off easily.