Why not prune Clematis in autumn?

Does anyone know if there's a good reason to wait until late winter to prune (certain) clematises? I have an old Clematis 'Jackmanii' which normally gets pruned later in the spring than it really should because I'm so busy then with other priorities. I'd like to prune it now while I have more time . . . actually I think I will.
What is the worst that could happen?

 

There is nothing wrong if you decide to prune it now. I have pruned my C. Jackmanii in the fall and in the spring, I saw no difference, except the place looks more tidy when pruned in the fall.

 

Back to gardens now ;)

did you make a decision?

I say try pruning now

And let us know next May!

one reason I keep some shrubs etc over the winter if for the little birds to shelter when it’s cold

they forage too, as I am sure you observe in your garden

 

I leave more and more shrubs unpruned and debris on the ground these days to provide food and shelter for birds and other creatures. I do like to support them but, to be honest, it's laziness too.

I am going to prune that clematis soon and will report back next year whether it seemed to be negatively affected or not. I suspect that the reason we aren't advised to prune certain clematises in fall is that there is a concern that it might encourage new growth at a time when the plant should be going dormant. Otherwise I have no idea - maybe it's just one of those bits of wisdom that get passed on generation after generation without anyone questioning 'why'?

 

Here, in Estonia, they generally suggest to prune Clematises in the Fall.
The aim of autumn pruning is:
1. To promote division of shoots
2. To supress diseases
3. Easier covering for winter for tender Clematises
4. Tidier look

Here unpruned Clematises are more like a sign of laziness.

You can verify this from the website of our biggest Clematis grower, Roogoja Farm. Their English variant of their website is very limited, but I provide you Google translation of the relevant Estonian page, see the "Wintering" section there. Keep in mind, that Clematis is translated by Google as "Thread of life", as this flower is called "elulõng" ("elu"= life, "lõng"= thread) in Estonian. The rest should be robo-translated so, that the point of the text is mostly understandable without additional comments.
Two methods for pruning are explained there.
Elulõngad | Elulõngade kasvatamine ja hooldus

 

I agree Margot - growing up with avid English gardeners on Vanc Isl

and neIghbor farmers who’d moved out fr Prairies

a lot of the old maxims do ring true

And I think same warning as you cite above - also went with Laurel hedges and Roses — don’t prune before winter because they’ll sprout tender new shoots and get frosted

(I realize one also considers the bloom on old or new wood (or both) factor)

and Sulev - that’s an interesting website - I remember one time we (via this forum) tried to figure out a close match in BC Alberta to your city climate

 

@Georgia Strait, Roogoja Farm is famous because of their Clematises and Nordic grape vine cultivars. They are ca 30 km from me, I have visited this farm number of times and brought some grapes and Clematises from there. They are further away from the sea, so they don't benefit from milder winters as much as me. It is amazing what they have accomplished there growing tender cultivars, despite such an unfavorable conditions.

 

@Margot - did you trim the clematis yet?

if you can - pls photograph and post before and after for our « citizen science » study

 

@Georgia Strait
Actually, I didn't prune it after all because most of the leaves are still green. I will photograph it when I do and keep you posted.