Hello Rema,
I also bought my dahlia akita at Wal Mart and planted mine in a pot with the sprout pointing up. I did not bury the sprout. I left the potted dahlia in the shade for 2 weeks for it was already during the summer time when I bought it and it was over 100 degrees in my area then. During summer time, in my area, it is ideal to have the dahlia in full sun in the mornings and shade in the hot afternoon.
Mary Ann