First, it is never a requirement to prune clematis although most growers do, just to keep the vines tidy looking and avoid creating a big tangled mass of dead vines. And while they may all look dead now, they should be coming to life. If you examine the vines closely, you should see the beginnings of fat buds emerging along the sides of the stems.

You could prune them all back to about 18-24" but not knowing exactly what type of clems you have and how well established they are, that may be more than necessary. Clematis are divided into 3 different pruning groups, depending on when they bloom and if they bloom on old growth, new growth or a combination. And each group is approached differently :-) Confusing, huh??

I think you have two options you could follow. One, do nothing. Just leave the vines as is (ignore the tangled, dead looking mess). They will leaf out in due course and after a few weeks of growth, the tangled mess will have disappeared under a cover of a new growth, followed by flowers. But keep note of when each vine blooms and if you like, come back with photos that we may be able to identify as to pruning group, if not a specific name. Then we can be very specific as to how and when to prune.

Your second option is to examine each vine closely as described above, looking for buds and signs of new growth. Once you have identified this growth, then you can carefully remove any dead portions above any point you wish to choose as a starting point. The larger, more established the vine, the higher on the vine will be your starting point. Obviously, if you have a big, mature vine with a hefty 'trunk', you don't want to cut that off at 18-24", but a newer vine with a just a few thin stems can take a harder prune.

This may sound a bit intimidating but it's really not. An established clematis can tolerate a lot of pruning without issues, even pruning more than is suggested for that particular group or at the wrong time. I would venture to say that your clems most likely belong in the group 2 or 3 designation and both of these will easily accept hard pruning and the only drawback may be a slight delay in flowering time for the group 2's.

btw, it is very helpful for us in responding if we know where exactly you are located. You can change your Houzz profile to include either your zone number and/or a locater note (like my PNW zone 8/9).

Thank you!!! That's very helpful! I'll try to change my settings, but as an FYI, I'm in zone 3 :)

Ahhh.....zone 3 would explain why your vines still look dead. :-)) In warmer areas, most clems have begun to leaf out and some are even blooming (much due to some weird spring weather in various areas). But I'll bet yours will be showing signs of life very soon, if buds not already present and beginning to swell.

Sarah, here's how to change your profile to get your zone to post by your name automatically in GW:

Go to Your Houzz in the upper right of every page, click Edit Profile, and on the left side click advanced settings. Well down the advanced settings page is a blank labeled Climate Zone for Garden Forums.

If you add info on your state/province or the nearest large city you will get even better information since zone only relates to average coldest winter temperatures.

Then return to the top of the page and click Done Editing.

Here on the northern edge of zone 5 my vines have swelling buds but nothing opening yet, so you have a few weeks yet before you see buds opening.