Thanks guys. That was kinda my thinking, but... I gave it a try a couple weeks ago anyways (had some rhubarb in the garden). Inspection this week showed no sign of the leaf in the hive at all. Not even a little piece of stem left over. I did not notice a big increase in litter on the bottom tray, so they must have been taking it away from the hive.
I believe it was the Oxalic acid in the leaves that was suggested as the reason for including it.
Thanks again.
- K