I think I have Sweet Autumn. It came from a mislabeled box from a big box store. It dies to the ground every year and covers a 7' obelisk by September. I've had it for about 8 years now. It's manageable, but definitely vigorous and tall.

I think that the question is referring to invasiveness in terms of seeding around, not plant size.

I have grown SA for years and never had a seedling.

Thanks all for your response.
As nhbabs said, I was referring to the seedlings and not size.
Great mnwsgal, I can go ahead and buy it then :)

- Bob

While not officially listed as "invasive", it is categorized by the US Forest Service as "of local concern" and should be monitored.

It is of importance NOT to take anecdotal experience as a guide to invasivness - many times plants can be and are considered invasive yet not be evident as such in a garden setting. That doesn't mean the seeds are not dispersed far and wide by wind or wildlife.

Here is a link that might be useful: USFS Section 3B invasive plant listing

It is not listed as invasive or of future concern in MN by the U.S. Forest service.

Did you look at that link? It IS listed under Category 4 - 'Of Local Concern and Monitoring'. And Section 3b of the forest service certainly includes MN!

btw, the common name they assign the plant is "yam-leaved clematis" but C. terniflora is most definitely SAC.

Thanks for the list and concern.
It forced me to check all the invasive plant lists possible in Canada, where I live.

And I couldn't find SAC in any list, from BC to QC.

It is an interesting subject, the invasive species. Sometimes native species can become sort of invasive. We had a virginia creeper, a native plant in Eastern Canada, in our garden, and each year, I had to remove, tons of seedling growing in our garden. As the seeds are propagated by the birds that ate the fruits.

Well, I got so sick and tired of it, that I cut it down.
It was a tough thing to do, as I really liked this vine, as it turned our sun room into a tree house :)

The thing was that it had vines all over the place, under the eaves. So, it could be rather destructive.

I didn't want to replace it, with another vigorous vine and repeat the same mistake, all over again.

Yes, I did look at the link. It is a compilation of all the information from the several different states. That does not mean that everything listed is a concern in each of the individual states. I checked the USFS page for MN as well as various other sites regarding MN invasives. Clematis terniflora is not listed on any of those sites. Perhaps it will become a future problem but at the moment I have not found it is listed as a future problem here.

I did invasiveness research on this plant 15 years ago when I first planted it and have again as have lost 3 plants over the years and rechecked the info before replanting.

I agree with your comment that anecdotal experience can be misleading and that invasives are often carried by the wind or other means so that the original site owner is unaware of the invasiveness.

true-blue, Sweet Autumn is a vigorous vine. I don't know if it will grow under the eaves but believe it is listed as growing 20ft or more.

Here is a link that might be useful: USFS Invasive Plants MN

Thank you for the links gg148 & mnwsg ~ bk-marked & will go thru as I've been trying to allert as soon as I find one such as Dame Rockets included in *Mixed Perennial Seeds* packets yrs ago, Porcelain Berry (as I searched for a climbing vine for an obelisque) & Arch Angel Lamium I grew & spread like nobody's business (Kadzu-like in the N Eastern States)! SAC is not listed here as well but ...

True-blue my 7 y/o SAC (relocated many times around) tho not invassive, has produced seedlings & I feel as g-g148 suggested should be monitored!

FWIW

Another Question:

Does Sweet Autumn need full sun or will it flower in part sun/ shade?

I was confused by this news as well. I have had my sweet autumn for 4 years now. It has always bloomed heavily and outgrows the 13ft. trellis I have it on. It has never produced shoots, although the little seeds are everywhere I'm sure. My sister in law whom I haven't seen in a number of years and visited me recently,spotted it and warned me over and over about the invasive nature of this clematis, as she herself has one and battles constantly to keep it in check. I was beginning to wonder if we do indeed have two different varieties or if it is our prospective zones. She is in zone 7.

You're right, I've noticed people living in Zone 7 above, always seem to be battling, vines and plants, which are quite tame in our colder region.

I remember when I bought the New Dawn rose, people in zone 5, where warning me about a humongous monster, whereas mine after 4 years is a miserable twig, far from being the case :)

That's why, thanks to this forum and common sense, we can grow fabulous plants on our zone.

BTW is yours in full sun?

Mine is yes!

Hi, in answer to your question about shade and sun requirements, It can grow(and does right up next to my house under the eaves just fine and I remember seeing a post somewhere about it growing well in shade .
roseberri. By the way there are two different species that are sold as Sweet Autmn Clematis, one is of Japanese origin and one is a natives species there have been numerous debate over them and if you look it up in the past posts you may find it.
roseberri

Thanks cateyanne, and thanks to the detailed response roseberri.

Anyway, I ordered mine, and will get it sometime in June.
I don't have a full sun spot in my Garden, it's mostly shade/ part shade/ part sun. So, I have 2 months to decide where to plant the beast, Then 3 years to wait. Sigh !