Who or what is destroying my newly transplanted indoor plants to the outside garden?

Within a week of transplanting my geranium and hydrangea from inside potted plants to my outside garden, they have been destroyed by something that cleanly cuts the stalks of the plants. It looks like someone has taken a sharp paring knife and made clean cuts down the stalks. I used Miracle Gro on the geranium and Mir-Acid on the hydrangea after transplanting. HELP!