Question
hello.  i have 2 curly willows approximately 15 feet away and would like to have them arch together to create a 'natural arbor' - i'm also interested in 'living fences' -- any recommendations?

Answer
As to letting the willows grow together for a natural "arch", I think you've picked fine plant material to accomplish this.  It may take a while for them to grow together, but they can get upwards of 30-feet tall.  Bbent over in an arch would be much less, of course!

http://www.naturalfencing.com/images/additional1/177_resized.jpg
http://www.theecologycentre.org/assets/images/Willow_tunnel.JPG

I抦 sure yours will be much nicer than these two quick pictures I grabbed off of the internet.

As to "living fences" here is a link:
http://landscaping.about.com/cs/hedgesfences/a/privacy_fences.htm

The hedge-rows of Europe actually took up quite a bit of space, but were very thick and impenetrable to only the toughest of garden pests (and specially equipped allied tanks!)

If you are refering to vines growing though an established fence or frame, there are even more possible plants you could use - Climatis, morning glory, night-blooming jasmine, to name a few out of thousands of possibilities.

~Marc