Stuff should be dead and dry and caliper will depend on hp. Though actually, OH found some green wood chipped up easier. The manual should say. Ours does handle some green stuff though, like fresh cedar hedge clippings. Don't put through anything that is alive, invasive and might regenerate from little bits. Check on that vine in case it is one such. Ours bogged down a bit on a big pile of leaves that were a bit wet.
LOL, OH got a new chipper last Fall. It is a heftier motor so will handle more than about the one inch diameter our current one does. Even better, it was FREE. That's because it didn't work. Well, it works now and it does a good job. Come to think of it, the first one was a pretty good price too. A local guy won it in a raffle and because he had recently cut off his big toe using his lawn mower his wife said no way was she letting him keep the chipper. BE CAREFUL with the darn thing. WE never let Oban out when the chipper is running, for fear he'd stand in front of the out chute.