Mine is in mostly shade. The only sun it gets is late afternoon. Maybe that is what makes a difference. I used to have a G. phaeum Samobor, and that had the dark markings on the leaves, similar to your picture, but didn't have the lighter at the center of the leaves. Unfortunately the Samobor only lasted for a couple of years then disappeared. The Springtime has been coming back for 5 or 6 years now, and is slowly increasing in size!
