grow back
To return to a previous length or degree of growth, as after having been cut or trimmed. I know you're not thrilled with your new haircut, but don't worry, it's just hair—it'll grow back. When do you think that part of the bush will grow back? I didn't realize how much it was hiding our ugly porch.
grow back
[for something that has come off] to grow back again. (Includes parts of plants and some animals, fingernails, toenails, etc.) The lizard's tail grew back in a few months. The leaves will grow back in a month or so.