I have built wooden "frames" for many of mine. I used 1/2" square slats, cut them to length, and wired them together into the shape I needed. I left them to go naturally grey and they blend right in!
Also for some of the single plants - Iris, lily, etc. I have about 3' length of heavy weight wire that I have then made a small circle at the end of and flattened it to a right angle with the rest of the wire, leaving an opening to put the plant stem through. Just stick your wire in the groung, and the circle around the stem, and it's stands up!