Not now - the winter will knock it back, and if its really cold, it may even disappear underground. Wait till growth begins in spring, then prune back to new growth.

Passion flower can be cut back in late autumn after the growing season as well as early spring, but pruning in autumn is dependent on a number of things.

1. The type of passion flower you have.

2. How cold the winters get.

3. How established your vine is.

I'm assuming that you have a Passiflora caerulea (blue passion flower)? This is the most common species sold over here as it's one of the hardiest. I had one of these that grew rampant every year and I hacked it down virtually to the ground around about this time of year and it always came up with a vengeance the following spring. I personally think that pruning it this time of year helps growth the following growing season.

If you're vine is in a place open to the elements, not a mature plant, or you have some doubt, then prune it in early spring to be safe.

Prune all last year's side shoots to 4-5 buds in December when it is dormant if you want flowers next May. If you cut everything back in early spring you will lose the flowers. If you want to prune drastically then wait until late May after flowering when you can knock it back hard. Train and tie in the new vigorous replacement stems as they come up, removing only the excess ones. You may have to wait 2 years before it blooms again as year old side shoots need to form from the new stems.