Not cutting back a type III clematis which is what SAC is, will eventually result in a plant that has woody lower stems without any leaves. The flowers will also develop higher and higher on the plant. I normally cut all my clematis back in late December in my zone 7a NC garden and would advise you to do the same.

Thanks.

In a colder climate, I'd delay that cutting back time to late winter, like March. Even in my very mild zone 8, one can experience damage to exposed plant tissue from late winter cold spells if pruning or cutting back is undertaken too early. The "rule of thumb" is to prune both clematis and roses when forsythia blooms in your area.

Gardengal, haven't ever had that issue in my zone. I have cut all mine back in zone 7a in late December for the past two years and never had an issue. We often don't get our "cold" weather" well into January. If the plant is a type III, what does damage to exposed plant tissue matter since the plant can always come back from the crown if it is hit hard? If the tips of the plants are hit by the cold, then the buds further down the stem will not be affected. In fact, in the colder zones, the plant should be well dormant and not have to worry about the cold and being cut back in early winter.

Miguel, your points are all very valid, however almost without exception in clematis references does it state that pruning of group 3's should be done in late February or early March. Why specifically I'm not absolutely sure, except that pruning in general (for any kind of plant) should be done after, not before, any climatic stressors like winter cold or summer heat and drought. This timing makes sense obviously for group 2's as new growth/bud development should be apparent then and one can remove any obviously dead wood.

And while the ICS recommends a late winter (Feb/March) pruning for group 3, I guess one can take these specific recommendations in the same vein as one takes any clematis pruning recommendations - they are guidelines only and what works for you works!

FWIW, I pruned an extremely well established montana (20+ y.o.) late last summer and unfortunately it did not come back after the terrible winter we experienced in the PNW last year. Since I have pruned back this same vine numerous times at about the same time of year with no ill effect, I have to assume winter cold did it in.

Here is a link that might be useful: ICS pruning recommendations

Gardengal, I am shocked!!! LOL You who, in the past, have stated that the pruning rules are just guidelines and now you reference them as if they are written in stone!!! LOL

Rules are guidelines for the neophytes to follow when first beginning any new endeavour. With experience we all learn things we can and can't get away with in our gardens whether it be with clematis or any other plant.

As for your montana, being a scientist I would have to suggest you are jumping to conclusions with your conjecture and it is not based in fact and as you state is an assumption. Perhaps the winter cold did it in and not the pruning. One experience with anything is not enough info to make such a decision that the pruning in the late fall is what did your montana in.

Secondly, I would never have pruned it in late summer in my zone or your zone. Late summer pruning, especially on clematis as vigorous as a 20 year old montana, is going to stimulate massive growth at a time that the plant should have begun slowing down its photosynthetic activities and not having to rev them up to try and regrow all the top growth you have cut off. If anything the plant should have been saving energy reserves to get itself through the winter. Perhaps your cutting back and the resultant rampant regrowth zapped the plant's food reserves and this, along with the bad winter conditions, is what did your plant in. This would be even less advantageous in your zone since this stimulatory effect would have made your clematis actively growing later into the season and subject to any early frosts or adverse winter weather conditions.

My point with pruning clematis in the late fall/early winter has been espoused many times but I think that it needs to be made again. IMO, the colder the zone you live in, the earlier the plant in question is going to become dormant and the earlier the plant can be pruned. Once the plant is dormant, pruning will not stimulate regrowth like it does during the normal growing season. In the colder regions, the existing branches are going to be partially dead and not likely to still retain live tissue that can get hurt by being cut back (talking about the type IIIs that tend to die back quite frequently). Pruning back such dead plant material is not going to result in plant tissue issues because the tissue is already dead or dormant.

In my zone, I am more concerned with pruning back plants in late winter for the simple fact that I never know from week to week what the weather may do. We have had freak warm spells in March that would have caused the plants to break dormancy if I pruned then, causing the plant to think it is time to become active and only to be bitten back by the cold weather that always seems to sneak back up on us. This year we even had hard frosts on Easter.

In your zone and in Jeanne's zone, where the temperatures are more moderate all season long and where winter may last for a month or two at max, I would advise people to wait until early spring to prune their clematis. In my zone and similar and colder zones, pruning the type IIIs IMO are best done when the weather has turned cooler, we have had frosts that have put the plants to sleep, and I have little danger of stimulating growth at a time that I don't want the plants to be growing. That time is late December for me.

LOL, Miguel!! You did notice my middle paragraph stated that this timing should be treated as a guideline in much the same way all clematis pruning advice is :-) You know I had to get that in!!

I'd have to say that my timing for pruning clematis is based on my training and experience of pruning in general and that is primarily behind my contention to restrict pruning of 2's and 3's to late winter. There are assorted reasons behind this practice, most of them with a sound horticultural basis, but of course much depends on the specific plant in question. FWIW, late season pruning has been found NOT to stimulate rampant regrowth, as biological factors such as the winding down of photosynthesis and approaching dormancy and day length triggers all work to counteract this more typical in-season reaction to pruning. As I mentioned, I had pruned this same clematis at a similar time of year many other times with no adverse response and there was certainly nothing that could be described as rampant regrowth occurring after this incident either. Who knows, maybe its time had come :-) The good news part of the whole situation is that it was growing entangled with an old climbing rose that I absolutely detest so now I can remove the whole ball of wax and start over. I've got a 'Boughton Star' that I've been looking for an appropriate home for and this may be the perfect setting.