What is the fabric covering it and what is the length of the pipe and what gage is it? I have often thought of using one of the Redwood trees for a bender for a large radius. We have some old stumps that are 12 to 15 feet in diameter and there is one right next to our little green house.
For my application, I'm going to use plain suncloth over the top portion, and chicken wire along the sides and ends. I feel that a little shade during the hottest part of the day, and protection from deer and rabbits will be a winning formula.
The pipe is standard 1 3/8 toprail fence pipe available at Lowe's, Home Depot, or any home inprovement store. Your redwood stumps sound like a good option for bending the pipe. Just make sure you use an extension when bending the last 3-4ft.