We just completed a project recently installing a beautiful flagstone patio and we built a large wood trellis using Surface Heart Redwood.  We installed this for a customer that we have done projects for in the past and who is also uses our landscape maintenance services. Check out how they turned out! Plus I added a few links for some prefab trellis that are available to you. Not the quality of what we had done and of course more costly!
They were extremely happy with the project!