Doesn't matter what you find as you'll never really know what coating, or material, is on the inside. You could transfer cadium poision into the ash with the wrong material. Safest bet is to buy a cheap saucepan at the grocery store, usually about $5.00, and use it to burn your vines. Don't know whata your situation is but in my case I would fill it with pieces of grape vine and then sit it in my wood stove with a good wood fire buring. That would certainly incinerate anything in that pot but be careful you don't melt the pot.