The exact application would be to arch over a long dining table in a courtyard in eastern-most New York. The two rows of trees would need to span approximately 25' at a height of less than 15' or less.
Our candidates are:
But these are not based on feasibility at all.
Are there others we should consider? Or exclude from our list?
You want young horizontal branching trees such as oaks. Hey I'd try Golden Hops! This plant is so gorgeous and FAST...you can expect coverage almost instantly!! Stand back or get assimilated!! Flowers are late in the season and pretty little lanterns...are you into making beer? We've had great luck making beer out of this 'Sun Burst' or some similar named variety...the leaves are gold/lime green until the fall where they turn more green. In the spring, wack all vines down and pull old vines off structures. Trust me, this plant will cover anything you've got!! Easy to maintain...pleaching trees is a heck of a lot more time and expertise!!
Of the plants you listed, Wisteria will achieve coverage significantly faster than any of the others. Unlike the rest of your listed plants, Wisteria are woody vines rather than trees. If you provide them an arch to grow on, they'll gladly go right up it with only a little training to get them started. You will however, want to prune off any excess lateral growth if they start to try growing off the supports. Left to it's own devices, Wisteria will try to take over the neighborhood. Faithfully pruning back the unruly growth will solve this. The flowers they put out in late spring smell wonderful and conveniently they hang down from the vines, so they'll be visible from within the arch.
Another interesting candidate for the list would be Trumpet Vine. They are another woody vine and are similar both in their willingness to climb up any provided structure AND in their willingness to take over the surrounding landscape if you let them get away with it. Once again, pruning will keep them under control. Trumpet Vines flower in summer on till fall with large orange or red colored trumpet-shape flowers. For added fun, they are a favorite flower of hummingbirds. If Ruby-Throated Hummingbirds take up residence in your neighborhood you will likely be their new favorite feeding ground, which is it's own entertainment.
I'd recommend Hornbeam, already on your list, but Carpinus betulus, the Common Hornbeam instead. It's highly tolerant of being cut and trained, hangs onto its leaves in all but the severest of winters, tolerates windy and wet conditions and heavy soils, won't need a machete or a ladder and ties every month during the growing season like Wisteria or other climbing plants, and won't drop sticky sap all over everything so long as its not got a scale or aphid infestation. In the UK it can be bought fairly mature and ready pleached, not sure about where you are. General nfo about the tree here
http://plants.hicksnurseries.com/12170001/Plant/71/European_Hornbeam
and instructions for pleaching further down the page here
