I've planted a couple of Jackmanii Clematis at the base of a big cedar tree, in hopes it would climb at least to the point where the trunk forks out into major branches. I attached a couple of wires in zig-zag patterns to the trunk, since the vine didn't seem inclined to grab the bark of the tree, and placed the vine under the wires. I'm considering adding some sort of mesh for the vine to grab, since the wire I've got now is essentially 2 single "strands," and I'd like the vine to spread across the trunk. I'd like something that doesn't visually stand out. Is chicken wire my best option, or is there something else I can attach to the trunk that would be better suited to the need at hand, and last for several years without rusting?

Any wire wrapped all the way around the tree can eventually girdle it and kill it. And then you've got wire in the tree, complicating taking the tree down. If you're old, like me, you may not care about that because you won't be around 20 more years.

Clematis likes to climb rough barked trees and support structures/trellis less than an inch or so in diameter. The zigzag wire you have installed already may be just fine. Or, it seems like I've seen some black nylon synthetic "chicken wire" at a garden center.
Did your clematis have a bamboo stick in the pot with it? That helps it have a head start climbing the tree.

I used green braid fishing line. Its kinda stiff. I was able to arrange it and it last a long enough time for the plant to grow. Them i weaved the plant in its own established self.
Im wanting to do another here at my new home ....maybe this will kick start the project !

I did start the vines off using the bamboo ladders, and slipped the tendrils under the bark in some places. I've since removed the ladders, but it didn't seem to be doing well at all on grabbing the bark on it's own. Also, it's pretty common for pieces of bark to fall off this cedar tree, so it doesn't seem a stable primary thing to be anchored to, at least while the vines get established.

Good point about the tree growing and expanding. I wouldn't put chicken wire all the way round the tree, so it wouldn't completely girdle it, but it could be a problem if it's wrapped half way if the tree presses against the wire and ultimately cuts some of the vines in the pinch.

Regarding fishing line, I actually considered that, as I have green braid, but I'm wanting something that will last years, because of the problem with the bark peeling.

The synthetic chicken wire is an option, but kind of a waste for me to buy 25 ft. when I only need 5. I think for now I'll add more zig-zag single wires.

Thanks for the input!