About two weeks ago, I purchased a healthy forsythia shrub about six feet tall. It was in full bloom. I immediately got it home and placed crushed rock in the bottom of a 1/2 whiskey barrel and then proceeded to fill the barrel with potting soil and peat moss. The potting mix already has fertilizer, so I didn't add anything else to it. I planted the root ball (burlap removed) at a height where it would not be planted below the crown of the plant. Watered it very well. Leaves began growing after flower fell. At least I thought it was doing well.

Main reason for this post is that after a heavy rain we received last night, today it has begun to wilt. It's not even hot here. Maybe 64 degrees today. What did I do wrong? It seemed to be doing fine up until today? Was it the heavy rain or do you think that it needs to be watered more?