Some clematis that used to thrive are being increasingly shaded, year after year, by a nearby growing honeylocust tree, and are naturally smaller each year. They still reach the top of the 6' fence but without the bulky overhang they once had, and have only 20 or so flowers each year. I believe I have a few years before they stop blooming completely.

I'd like to move them to a new spot - but as safely as possible with the least chance of loss. Since they've been in the same spot for so long, they have basically divided and have some stems coming up 8 inches from other stems, so I would like to divide the plants and move half, so if it doesn't take in the new location I have another shot when moving the other portion. Also, by moving half I have another year to enjoy the established plant while the moved portion grows in the new location.

I've read that the best time to move clematis is in the early spring. Can I also do it in fall?

I don't know the varieties, but as far as I know they are very generic types that you find most commonly; nothing fancy or rare. One has a plain dark purple flower and the other is the same but violet.

I have searched extensively online for transplanting/propagation tips and haven't been entirely satisfied with the specificity and consistency of the advice, and I have a couple concerns.

1) I want to move them while disturbing the surrounding garden as little as possible. How much do I have to dig? Especially considering that I can't dig into/under the fence so will lose some roots there.

2) How safe is it to move them in the fall so I can see if it worked and get another shot in the spring or next year?

3) Can re-planting broken roots be a way of propagating them? Do root cuttings work?

4) If I move half the plant, how much of a risk does it pose to the remaining half? I figure they must be somewhat tough since they've lived so long, but I don't know how tough they are when it comes a move.