I forgot to mention that I've been checking out http://www.clematis.com.pl/wms/wmsg.php/1034.html. Based on your recommendations, will I be able to find/buy the clemantis you recommend in the DC area or online/catalog?

Samzen, you can order clematis from Dan at Brushwood Nursery in PA or from Debbie at Silver Star Vinery. Both sell a multitude of varieties. Web addresses for both are located below.

I have over 100 clematis in the ground and don't have any that get to your 15 foot requirement. Many may reach 10 feet or so tall but few of the common varieties will reach 15 feet tall, especially not in any short period of time except for sweet autumn clematis (clematis terniflora) and clematis virginiana. Both of those varieties are way too common and for your structure I would go with something big and grand like any of a variety of the montanas.

Check out the following link at the bottom of the post and enter Montana into the first field entitled "Clematis name includes:". You will get a whole list of montana clematis that you then click on to get information about. Those with a + by the name indicates that there is a picture. There will be info about eventual height listed in meters but you can convert that to feet by multipling the # of meters by ~3.28. A lot of the varieties are not available in the US but Dan at Brushwood and Debbie at Silver Star Vinery do carry several.

Brushwood Nursery
http://www.gardenvines.com/catalog/index.php

Silver Star Vinery
http://www.silverstarvinery.com/

The montanas are early spring bloomers but I think they would look smashing on your pergola and many will easily meet, if not surpass, your 15 foot height requirements. If you are in zone 7a, then they should be hardy and bloom wonderfully for you.

Here is a link that might be useful: Clematis on the Web

My Jackmanii is over 10' and has run out of arbor to climb! The vines spill back over to the back side. It is about 5 yrs old.
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As you can see, I need to prune it short to get the lower growth to fill in. I pruned it back last year and much of the lower growth ended up on the wrong side of the arbor this year!

Are you trying to shade in the entire perogla? I think that Sweet Autumn is a pretty vigorous grower, but some consider it invasive. Maybe you need something that vigorous to cover your space? Hang tight and I am sure you will get more answers!

Samzen, another option that I thought of today. Plant one of the more vigorous montanas on one post of your pergola and allow it to cover the entire top portion of the pergola and adorn the other posts with clematis that will cover up the posts themselves and that won't have to get 15 feet tall. That way the choices expand greatly.

That is a good idea. Debbie has some of the Montanas that have slightly bronzed foliage and pink flowers rather than green and white. More interesting IMHO.

Yes, she does. I went back and forth between getting Broughton Star vs. Worwickshire Rose for this fall. I was tempted by the doubles of BS but the foliage of WR was also appealing. The doubles won out and I told her to make sure she held one for me. Now I am jumping back on the fence and contemplating them both!

I do not have room. Sadly. Montanas grow huge here.

In his book entitled "Clematis--The Montanas-A Book for Gardeners", John Howells talks about using trees and conifers to grow montanas through. He also talks about running rope, chain, or wire between two or more posts and having the montana climb up and along the wire from post to post. I have thought about trying something like that!

He also talks about a Hill House montana support which he describes thusly (with my paraphrasing):

A 12 foot post, rot proof, is purchased...The same source will supply 9ft. roof slats. The slats are cut into 3 foot lengths. These are nailed at intervals to the upper 9 foot section of the post. A three foot hole is dug and the post is sunk into the hole.

Thaks you all for your help. It sounds like a Monatan vaqriety will get to and cover the pergola, while then I can plant seveal other varieties to climb up the posts. Nice idea! Again, thanks!

We want to see pictures Samzen when you get that pergola covered with blooms!

Will do, but that may take a few years... you guys know better than I. In the meantime, I e-mailed Dan and Debbie. Depending on how they respond to my e-mail I'll go with one over the other.

Again, thank you all!