A cute label in the pots is only the first step. If this is a live auction (vs silent auction), the auctioneer can make or break it. In this sort of situation I presume an auctioneer is a volunteer. The more entertaining the better the bids will be.
I was auctioneer one year for our garden club, the plants auctioned were the ones that didn't sell outright at our street stands. Let me tell you I had never done this before but all kinds of baloney malarkey spewed out of my mouth in the most amazing way (if I say so myself). It all went well and we made lots of money which we used to operate a soup kitchen garden.