Usually people use 2"x4" 14 gauge fencing (4' or 5' tall) for fencing in individual trees. It is stiff enough to stand by itself and just needs to be staked to keep it from blowing over. wire mesh fencing (aka "wire cloth") is usually 1/4 to1/2" square being quite flimsy, would need to be staked on 4 sides.
Most young trees do not fare well in deer populated areas without fencing for protection. I'm not sure how well deer like willow, but they pretty much browse everything in my area even with food plots around.
I use 2"x2"x8' polypropylene fencing for multiple trees.
I get it from Deer Resistant Landscape Nursery in Clare, MI.
http://www.deerxlandscape.com/cgi-bin/webc.cgi/Fencing.html