nothin against that method GK, but what i usually do to get um out as stress free as possible is:
1. Take sissors and cut from the top to the bottom of the container on 4 sides.
2. Peel away the container very gently and grab the whole wad of dirt with your hands and plant them in the hole the you have PREVIOUSLY prepared.
In order to prepare the hole, just take your yogurt container and fit it into the ground before you take the plant out of it.
Peace