Welcome, Kas300. The flowers of your Clematis montana rubens come directly off last year’s ripened wood (meaning wood that was developed last year and is now a year old), so if you prune now, you’ll lose whatever bloom is going to happen in 2008. Best time to prune the clematis in this group (the ones that bloom on the previous season’s wood, including the popular ‘Jackmanii’ and ‘Henryi’ and the beautiful small-flowered viticellas and alpinas, among others, is just after bloom. So wait, then clean out the plant to get it back in shape so the rest of the season it can produce new wood that will then ripen and bear your blooms for next year. You’re basically going to be thinning out dense areas, heading many of the tangled side shoots back to where they originated, and taking out dead and damaged wood wherever it occurs. You want to end up with a logical framework for the plant to regrow from–a balanced basic shape that will fill in nicely and support growth from some well-placed main stems. I can’t explain this from here, except to say to stand back, take your time, and observe how the plant grows so you understand what to leave and what to remove. Sometimes the plant is such a mess you may prefer to cut it way down, less than a foot from the base. I have lost plants this way…and also had them come back better than ever. Either route (but especially the drastic one) you will want to wait to perform the surgery till after bloom, as I said, and keep the plant well-watered this summer as it recovers.