What is the difference between ordinary Gastrodia elata and "Mingtianma"? Are they two different varieties?

After harvesting Gastrodia elata, select those that are large, uniform, and have a red "parrot's beak," wash them in water, peel them, boil them (adding alum water), shape them, dry them, and then fumigate them with sulfur; in this way the color is good, and through this fine processing "Mingtianma" is made. Most of those supplied for export are called Mingtianma. Gastrodia elata and Mingtianma are the same variety; the only difference is that the processing is coarse or fine.