Don't know who Grubb's is and what the mystery part means. This my first real Green tomato. Have no idea when it will be time to pick it. I know it a big tomato now and I so want to pick and make some green fried tomatoes, but have to wait til I have lots on the vine. Hopefully when the time comes, I'll be brave enough to taste test a green one. If not will just be more seed to save.