I asked this same exact question a few weeks ago and did not receive a response. There is no way to right click the spells because they do not appear in your spell book. You cannot sell them anywhere. Your only choice to get rid of them is to use them and waste your energy on gardening tc you don't need to use. So here is what I did to get rid of them. I had over one hundred of them clogging up my tc backpack. I created a dummy wizard. One I would not really use. My dummy became friends with one of my other friends in wizards. I gave my friend all the garden tc I would not ever use. I then went on to my dummy wizard and found my friend. He then gave my dummy wizard all the garden tc. Now my dummy has them. When the dummy gets full of these gardening tc then I will just delete it. I could not figure any other way to get rid of them. I really wish they would fix this problem, but oh well, I just had to come up with a creative way to do it myself. Hope this helps.
I asked this same exact question a few weeks ago and did not receive a response. There is no way to right click the spells because they do not appear in your spell book. You cannot sell them anywhere. Your only choice to get rid of them is to use them and waste your energy on gardening tc you don't need to use. So here is what I did to get rid of them. I had over one hundred of them clogging up my tc backpack. I created a dummy wizard. One I would not really use. My dummy became friends with one of my other friends in wizards. I gave my friend all the garden tc I would not ever use. I then went on to my dummy wizard and found my friend. He then gave my dummy wizard all the garden tc. Now my dummy has them. When the dummy gets full of these gardening tc then I will just delete it. I could not figure any other way to get rid of them. I really wish they would fix this problem, but oh well, I just had to come up with a creative way to do it myself. Hope this helps.
Open your spell deck (P), click the little gardening icon above Treasure Cards. Now pick the Treasure Cards icon from the Gardening Spells page. Then you can destroy cards there.