Sure you can do it.......it's just a matter of good timing. Since Jackamanii is a type 3 or hard prune clematis, swapping out trellises when you prune is the ideal time. This is usually done in later winter (end of Feb/beginning of March) but some folks have had luck doing it in fall.

I agree w/ gardengal, just do it when you prune! :o) It will grow back as normal next spring!

Thanks! I will have to read up on clematis pruning. I am new to this climate zone, and have never lived where there is a real winter. For reference, I'm in Colorado and every bit of my plant and gardening knowledge is from the Bay Area and Phoenix. Vastly different.

Anyway, we bought the place in December and nothing had been pruned, so I left it. Just observing everyone else's garden, that seems to be the practice here, as I guess it helps protect vines and perennials from freezing?

But if it can take a hard prune in the fall, I'll do that.

No, don't prune it hard in the fall. You are going to have to wait until next February....pruning encourages growth and you don't want growth right before winter. Even though Clematis are very hardy.

I grew up in Phoenix, have a greenhouse here in Portland to grow bougainvillea and the rest of the tropicals I miss.

Depends on how cold your fall temps are. In MN I prune my clematis the middle/end of November because there is not going to be any new growth until spring and most P:2 clematis die back to the ground. Sometimes I wait for spring pruning the P:2 plants that bloom double with first bloom hoping their will be some live vines left for new growth in the spring. Occasionally that works but mostly it doesn't.

I planted my clematis in 1977 and it’s beautifull, but is too big and heavy for my fan shaped plastic/vinyl trellis. I prune out most of the dead stems in the spring before new growth starts . Would that be the best time to replace the trellis?