The vines you mention are annuals. Are you restricted to those, or would perennials work? I have grown black-eyed Susan Vine AKA Thungergia, and it stayed well covered all summer. I am in a different growing situation, however, so I don't know how it would grow for you. It is a perennial in warm areas, but I think would be grown as an annual in DC just like NH.

Perhaps one of the perennial Aristolochia AKA Dutchman's pipe vines would work. I haven't seen a lot of them, but those I have seem relatively densely leaved. Perhaps there is somewhere in the DC area you can see one to decide if it fits the need.

If you have room, can you plant a line of medium sized perennials or small shrubs such as Amsonia hubrichtii or some shrub roses or smaller spireas to hide the bare stems? Or even plant a second set of vines to cover the bottom of the trellis.

If you don't get an answer here, you could try asking in the Mid-Atlantic forum since the Virginia forum isn't too busy. Another option is to visit the National Arboretum or the botanical garden on the mall to see if there is anything there that might work for your setting.

Confederate Jasmine espaliered. Here is a link. http://davesgarden.com/guides/pf/go/55230/

I'm fine with either annuals or perennials. I'll look into all these options, thanks for the information.