For some reason, not all dahlias produce viable seed. I've saved seed from different varieties, had excellent germination from some batches and absolutely nothing from others. I've also had really lousy germination from commercially bought seeds (0-5%).

My recent experience with Ferry-Morse's Unwin dwarf seed: of 72 seeds sown, fifty have germinated. Still have more in the packet for further seeding. The first four seeds showed germinating roots in thirty-five hours! They were sown three per peat pellet; situated near a southerly facing door. Temps have been optimum, I reckon. Purchased the packet at Lowe's this spring.