If thorny a Rubus sp.

Too fast for Rubus and wrong flowers. Looks like it might be an Araliad of some sort.

No, It is definitely not thorny. Here are some more pics:

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Sorry about the poor quality

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Could it be goutweed/bishop's weed? It looks like Aegopodium to me.

Here is a link that might be useful: Aegopodium podagraria

Not with vining stems. Leaves etc. are different anyway. Probably familiar to somebody from the region.

It looks like Virginia creeper (Parthenocissus quinquefolia). It is a vigorous grower, however it is native to a large range of North America and therefore is not considered an invasive plant. It likes to climb but will grow as a ground cover. Makes attractive purple berries on reddish stems. The birds love the berries and spread it around.

At the risk of ruffling more feathers here, are we sure this is
just one type of plant? Wouldn't be the first time two different
ones were growing together making ID's that much harder.

Hi there, I was ID-ing the plant with the berries forming in 1st pic and that "Thelaw" is holding up in the 2nd pic.

Virginia creeper often has gorgeous fall color up here in New England but our harsh climate probably keeps its growth in check somewhat. It is native to both MA and MS though.

I mean flowers in the 1st pic.

I'm not seeing any Virginia creeper in these shots. The only holdup is that somebody who happens to know this one has not come along. No point in grasping at straws before then.

So sorry, didn't think I was grasping at straws, just conversing. It looks like V. creeper to me (see link), got plenty growing in the yard too. But "looks like" doesn't mean that's what it is, so I defer to your much more learned opinion and exit the thread.

Here is a link that might be useful: Parthenocissus quinquefolia

No idea what it is for sure, it does resemble the V. Creeper growing in a shady part of my garden under some birch trees. The V.Creeper that has climbed and gets more sun looks a bit different though. It's only been in my yard two years and has covered 24 feet of fence and spread in the mulch like mentioned, the stems under the mulch appear pinkish in hue. Just sayin.

Entering this thread again, LOL! I hate to leave the thread and the OP in a state of confusion about this vine. The pictures in the links below hopefully help ID the flowers in the OP's 1st pic. IMHO, this vine is Virginia creeper, but perhaps it was confusing to ID because it is growing in the form of a ground cover mixed with other vegetation.

Flowers

More flowers

For the TS, a closeup of the flowers would help clear this up. The leaves look different than what I am used to seeing on Virginia Creeper but plants are quite variable.

Thanks to everyone who responded. I am 100% it is not Virginia Creeper. We have VC here and while it can be a bit of a nuisance, it grows nowhere near as fast as this stuff. VC's more mature vines are also somewhat "woody", but this vine is very tender everywhere. After ya'll pointed out the similarities between this vine and VC I googled "Vitaceae" (VC family), but found nothing of any use. This vine has yet to make any berries, fwiw.
I feel sure this stuff will get killed back with the first frost we get, but I'm sure that when it warms back up in the spring, it will come back from it's roots and continue its rapid growth. It's roots are tuber like, and I'm guessing that if someone were to try and till these vines up, they would have a bigger problem than before.
I think I'll post this in the "weeds" section of this site and see if anyone knows over there.
Thanks again for everyone's input.

I think it's Cayratia japonica.

Wow, Jaynine, that sure looks like it to me.

Here is a link that might be useful: bushkiller

I think Jaynine has it. Here is a link to some good pictures of it.

Here is a link that might be useful: Cayratia japonica.

Came upon it completely by accident. That last picture reminded me of a grape ivy houseplant I once had. While looking at images of various cissus, there it was.

Maybe your local agricultural experiment station can help you with the best way to eradicate it.

Same family as Virginia creeper anyway, that part at least was right. Otherwise it was clearly not Virginia creeper from the start.

Yep, Jaynine nailed it, unfortunately for me....lol. Although it's not really a laughing matter from what I have been reading. I saw Jaynine's post around 9:00 last night and then stayed up reading about Cayratia japonica ( AKA Bushkiller ) until about 11:00 and I still didn't get to sleep till 2:00am just thinking about what I'm going to do.

Thanks again to everyone, but especially to Jaynine. It amazes that she came upon it by accident and still remembered what it looked like.

Otherwise it was clearly not Virginia creeper from the start.

Clearly. To some people! ;) Thank you for pointing that out B boy.

Good luck with the Bushkiller. It sounds very invasive. It would have been lovely if it were V. creeper!

Clearly. LOL, look at figure H in the second link. Extremely clearly for identifying through photographs and not in person. I'm pretty touchy this morning not enough coffee yet...