GDP and Purple Urkle are not known for getting great yields. Not only that, you have to be very careful when training them because you can get some real larfy buds if you're not careful. I SCRoG mine and get ok results with a fixxed trellis mad of string. Thing is, the buds look really good and they are really dense, but they are also really small, and get smaller as they dry. The buds don't real get nice and plump like some strains when you double trellis them or even single trellis them. Add to the fact that you're probably only getting 1/2 ounce to 1 ounce of dried bud per plant and the bud you are getting tastes and looks really good for the most part, and people like it a lot because of the fruity taste except for 1 thing. The high is just really not that great. It is very lackluster high unlike a lot of more potent strains out there like OG and diesel strains. That is why breeders are always trying to cross GDP with strains like OG Kush and Chem Dawg and everything else. To keep the fruity purple flavor and stuff, but add a little more potency to the strain which is badly needed. Also, it is hard to get GDP to grow really large buds. Most buds are only about as big around as a roll out quarters when dried.