How do I tell if a rutabaga is fresh?
That is wax, it's done to help keep the moisture in the root. Turnips are also.

You know it's getting along when it gets soft and spongy or when the skin starts to wrinkle, same with turnips, beets, parsnips, carrots....You pretty much can tell whether they are good or not in exactly the same ways. Are the firm and crisp or soft, flabby and spongy?