yep, Cazzie hits the nail on the head. Your LFS are talking rubbish. Most Crypts tend to grow really slowly and don't mind a bit of shade. In Amanos complete works he talks about putting crypts in clumps under larger plants or stems, as they will grow out as the scape matures, and as stems don't tend to last forever in scapes, crypts do. I like to see Crypts planted close to each other, it looks more natural.