Man-eating plants for Halloween -- need help w/ ideas for main stalk

How tall? You can use rebar for the base and bend it. Wrap it in latex paint soaked cheesecloth and grape vine

I made a large sized eyeball and man-eating type plant a few years back. They were a little on the fun side put I used pvc and connecters with bendable pvc on the top to give them a rounded look. I recently had to try and make completely posable arms on a prop and used the diy version of store props. I bought a pkg. (you may have it on hand) of electrical wiring (sorry but I'm too naive to know whats it's called) that was thick enough to hold it's own and ran it through a dollar store pool noodle. This may work for what you want or at least an idea to improve on.

I was thinking no more than 5' or 6', with long vines coming out of the planters pot, but lightweight.

You can bend pvc with heat if you want a thicker stalk

All I can think of is maybe PVC pipe inside of pool noodles?