This just in: Upon review of her porch garden and a brief conversation with Mom, your humble correspondent has discovered that I did, indeed, plant my calla lily bulbs upside-down. A team was immediately assembled to dig up the lilies and re-plant them (me, some gardening gloves, and Pringles and Carlie for moral support).
Such a critical error in judgment (thinking the bumps were the roots and not the stems) has resulted in some very wonky looking calla lily bulbs. The stems were still trying to grow upward around the bulbs, and the roots had sprouted from the top, growing downward around the bulb as well. I am one ace gardener.
The situation has been rectified, sort of. The bulbs are right side up, but now the stem growth is pointed downward. I intend to rely on Mother Nature to sort out this whole mess, as it seems best if I henceforth just keep my hands out of the dirt on this one.
Stay tuned to see if I haven't wrecked the lilies entirely. :) Go me.