Q: My neighbor told me I need to prune my jackmanii clematis now. Is he right? How much do I cut back? This is a new plant for me and I don’t want to lose all those gorgeous flowers.
A: Clematis ‘Jackmanii’ belongs to the group of clematis cultivars that bloom on new wood (stems that start growing on the plant each spring). If left alone, the plant will become thin at the base, and over time it will be riddled with dead stems instead of the lush flowers we associate with healthy clematis.
Here’s a little basic clematis growing information. Clematis grows best in full sun or partial shade. It’s hardy in USDA zones 4 to 8 and likes moist, well-drained soil. You may have heard that clematis like their head in the sun and roots in the shade. This is best achieved with a 3-inch layer of mulch around the base. Mulch also keeps the soil moist, but to prevent stem rot keep the mulch about 6 inches from the stems.
The best time to prune jackmanii clematis is late winter or very early spring before the plant comes out of dormancy. Cut the stems back to about a foot off the ground, just above two strong buds. (See illustration) Leave two to four sets of buds per stem. You don’t have to make angled cuts; a straight cut will do just fine.
As the weather gets warmer and buds appear, train the new vines onto your trellis. This is your opportunity to space them so the flowers will show better.
You may have noticed clematis branches do not twine around the trellis. Clematis climb by twisting thin corkscrew shaped leaf stems, called petioles, around a support.
As soon as you see new growth, feed the plant with an all-purpose granulated fertilizer such as a 10-10-10. Following these simple steps you can expect to enjoy your jackmanii clematis for years.
Contributed by Eileen Tully, Certified Colorado Gardener. Photo and illustration courtesy of Park Seeds.
Pikes Peak Area Garden Help 
March 17, 2010 at 2:57 pm
Thank you for this information. I am looking for a fall/winter clematis that blooms around November and is all white…the fragrance is beautiful as well. I cannot seem to find this anywhere so I was wondering if you have a name for it.
March 17, 2010 at 3:38 pm
Hello Shirley,
Hmm….I wonder if you are thinking of sweet autumn clematis (Clematis paniculata or C. ternifolia). It is a rampant grower and is covered with smaller white blooms that smell terrific. In our area, it blooms in August/September/October timeframe (not too much is left in November). White Flower Farm has a nice picture of it at http://www.whiteflowerfarm.com/26630-product.html
Another good place to look (and ask) for information is The American Clematis Society at http://clematis.org/
January 30, 2011 at 12:09 pm
I planted a tiny sweet autumn clematis start ordered from Michigan Bulb catalog last year, and it grew unbelievably fast over a fence with a limited western exposure on one side and eastern exposure on the other side. It is simply gorgeous, smells like honey and the Japanese beetles didn’t touch it! HIghly recommend this clematis for fence coverage!
November 1, 2010 at 11:31 pm
Hi there, I planted this plant this year and luckily we had a great late fall as it did not bloom until end of Sept-Oct and just froze the other day. I live in Saskatoon and wonder if it will survive the harsh winters we get here, not sure of our zone number. I had a plant years ago and it bloomed for a few years and then one year it just did not come up, any advice would be appreciated.
November 4, 2010 at 2:44 pm
Hello Verna –
Well Saskatoon is in the USDA zone 2B for plant hardiness (meaning that the minimum temp in the winter can be -45degrees….brrr!), and the Clematis ‘Jackmanii’ is rated hardy down to zone 4 (meaning it prefers balmier areas where it might only get down to -25 degrees). So….if you have a particularly warm winter and mulch the plant well, you may have some success overwintering the plant. Otherwise, you might want to check in at your local garden center for some alternatives that would be hardy for you. Good luck!
Carey Harrington, Certified Colorado Gardener
March 14, 2011 at 2:07 pm
I bought a few jackmanii clematis last year and being that it’s March 14th and lately winter has been mild, should I prune it now? I planted them last July and they were very fragile……
Also, there are a few clematis already existing on a trellis in our new house and I don’t know what kind they are. They bloomed around the same time as the new ones. SHould I assume they are the same type and prune them as well? Thanks!
March 14, 2011 at 3:02 pm
Hi Julie –
I would say it’s safe to prune now. And I would also say your guess that the existing clematis must be of the same type (since bloom time is the same) and you can prune them as well!
Happy pruning,
Carey
July 21, 2011 at 6:02 pm
I followed advice and cut back my clematis in the late winter.This plant is 5+ years old and the vince grow very tall and spread, but no flowers. Any advice?
July 22, 2011 at 12:27 pm
Hi Terry –
Hmm….I wonder if you might have the type of clematis that blooms on “old” (a.k.a. last year’s) wood. If that’s the case, then pruning in late winter would remove the blooms for the following season.
You say your vine is 5 years old, so I’m assuming you’ve seen it bloom before? If so, do you remember what time of the year it bloomed? (spring? summer? fall?) If it bloomed in spring, it is the type that blooms on last year’s wood and you should prune it as desired immediately after it blooms. Then it will grow over summer and set the buds for next year’s flowers.
Another possibility is that it is getting too much nitrogen (in fertilizer), making it concentrate on growing leaves rather than putting on flowers.
Or if it IS one of the summer or fall bloomers and it’s gotten super big and messy, a severe pruning in late winter (which is the appropriate time) might set it back for a year and you should give it another year to recover.
Good luck with your clematis (and I hope I’ve helped)!
Carey Harrington, Certified Colorado Gardener
March 13, 2015 at 9:08 am
I have an established jackmanii that didn’t bloom at all last year. Perhaps I pruned it wrong. Is there anything I can do to encourage blossoms this year or have I wrecked it?
March 13, 2015 at 9:42 am
Oh Tami – There are so many reasons a plant may not bloom in a given year (hail, insects, weird freeze at the wrong time, etc). So don’t give up! They can be pretty resilient (even if you pruned incorrectly in its past). I’d say follow the pruning advice up in the article, and this is the time of year to do it. Then cross your fingers and hope your clematis blooms again for you this year. Good luck! Carey Harrington, Certified Colorado Gardener
May 4, 2015 at 4:46 pm
My husband pruned jack a little too harshly – back to about 6 inches. It ahd already started to grow and it looks like he cut off all the new growth. i can see a bit of green but no new shoots.
Will it come back next year?
May 5, 2015 at 12:30 pm
Oh dear – fortunately most plants are pretty resilient. You’ll have to take a “wait and see” approach, but it should not take too long for you to notice some new growth if it is going to recover. If you don’t notice any new growth in the next month or two, you will probably need to replace it. Good luck! (You might also look for some help/advice at the site for the British Clematis society – http://britishclematis.org.uk – unfortunately the American chapter disbanded years ago)