i know that the trumpet vine plant is toxic to chameleons because the juice or sap can cause dermatitis. but would i be able to use some old dried up branches after thoroughly cleaning them. since they are completely dried?
I wouldn't risk it. What I do is get a grapevine wreath at Wal-Mart or a craft store like Michael's and soak it in the bath tub in hot water until the vines are softened enough to unwind and then place them in the cage, attaching with cable ties. They dry out and stay in the position that you put them in, are super cheap, look great and each wreath comes with a variety of widths of vines which is good for your chameleons' grip
I use those fake vines on occation, especially with deremensis or baby veields. However, I wouldnt' use them with adult veileds, or melleri, or any veggie-nibbling species.
I bought a subadult female from a breeder that used them. She stopped eating a few weeks after I got her, and died a couple months later. Her stomach was packed full of the things. Swollen aboout the size of a golf ball.