The problem with all of this is...reality bites. Vertical checking increases the surface area exposed to weathering. Most treated lumber comes with a warning that should be read because it doesn't guarantee longevity; for that reason choice of lumber type is extremely important. In my part of the world, cedar lasts longer (and clogs saws). Osage Orange is also excellent (which explains why it's so hard to find...heavily taken for fence posts and nowadays some folks don't like the fall fruit.) If you have any control over your wood, make sure to choose logs cut from the center of the free with no sapwood. Fewer knot holes is better although the 'knots' will out last the other wood, but by then, hopefully, the structure will be covered with roses. And finally...how you set the wood in the ground is a major deal breaker. In some areas, wood in the ground rots. In some areas, what works in well draining sand doesn't in clay in the next yard. In some other areas, wood in cement in the ground rots. This is another of those instances where local knowledge is a necessity.

In Zone 5 wouldn't you get complete de-foliage? In colder climates, a rose that doesn't lose its foliage could suffer. It generally means it's continuing to grow on after the first frosts of Autumn, which weakens the rose. I suggest the Explorer rose, William Baffin. You'll get a lot of canes which could camouflage the wall in winter, and it will grow to the heights needed. Repeat flowering sporadically after the first big flush of flowers. Wonderful rose. Hardy. Gorgeous. Very disease-resistant. Full and floriferous. Hope that helps some. Oh, it's a bright pink and only lightly scented. Not a tradition tea rose shape. Forgive my shameless plug, but I'm attaching an article I wrote about this rose. I love it and have several in my garden. Wish I new how to get pics in the posts. Here is a link that might be useful: Canadian Explorer Rose, William Baffin

With Austins, it's very much a matter of climate, like phyllissteen said. So many of the Austin roses are mild mannered shrubs in the UK, but bring them to the southern US or California (or anywhere with more sun the Britain!), with the longer, hotter summers, and you get giant climbers and/or octopus arms. Also, some roses respond to being tied to a support by throwing longer canes, whereas if they are grown free-standing they can support themselves just fine. And I'm convinced some roses are just bipolar... If you search through older posts about Austins in California, you'll find that one of the most common questions is which Austins DON'T run away and grow into huge monsters.

Ramblers are not only usually bigger, but tend to have very pliable, whip like canes that can be easily trained. Many ramblers however are once bloomers. There are some reblooming rambling roses out there tho. There are a many climbing roses that also grow very large and have nice flexible canes, but many can have stiff canes that tequire more work to train. It seems your pergola is a very nice size and you have space for a very large rose or multiple smaller climbers. I would like to add another one for you to consider. Mel‘s Heritage is a very very nice healthy repeat blooming rambler. If you google it and find old threads you can see Lisa’s Mel that is magnificent and Jeri also has a gorgeous one. I have multiple of this rose because it is extremely healthy and low maintenance. It also can be wrapped about anything (just like a rope) 11 feet tall In less than 3 years . Please click to enlarge Another rose that comes to mind is Spirit of freedom. Helen posted a picture of spirit of freedom on her pergola and it is just stunning. It is a beautiful Austin and it gets pretty big.