If you're like me, you don't use treasure cards all that much.
The occasional Satyr when you're in trouble and you don't have one in your hand is about all the usage your treasure card deck gets.
Well now with gardening and Celestia, we're getting a lot more treasure cards.
In fact I keep maxing out my treasure card deck (or if you want to call it by it's proper name: "vault").
Well you can get rid of treasure cards you aren't using a couple different ways. First off, you can go to the Bazaar and sell them. You can only see non-enchanted cards though. Not really practical if you have a lot of enchanted ones. If you have a lot of enchanted ones or ones you cannot sell at the Bazaar like moon treasure cards, you'll have to "trash" them. You can do this by right clicking on the card...
...then a little window will pop up asking you to confirm.
You can rid yourself of all your unwanted, unused treasure cards and Harold Argleston's face popping up every time you get a new treasure card.