cpdunit1,
I think Seng does well in competition with most other wild woods plants.
No doubt there are exceptions to that, very invasive types. I have seen some poison ivy patches so thick that it would be very difficult for seng to grow in it, perhaps impossible.
I found a small patch of seng a few years ago growing in a very thick place, some poison ivy and other stuff was really crowding it. I cut the poison ivy and other stuff back and the seng is doing fine now. But not real sure how much that helped it out, because it was growing there anyway.
It looks better to me for sure (especially getting that poision ivy out of the way). I hate that stuff.
If you have the time, and are willing, I am sure it will be OK for you to eliminate the competition around your seng, especially in areas where it appears to be really competing with the seng as long as you do it in a way that will not harm the seng. Pull up vines and other plants roots and all. Just try not to disturb the seng plants or roots.
If it is only a small amount, I would not worry about it too much.
Nice little 3 prong in your picture. It was probably a 2 prong last year, and most of the plants I find like that around here are in the 4-5 year old range. It grows kind of slow here on my place (the wild stuff).
In the case of that one in the pic - I don't see any reason to clean up around it, nothing crowding it.
Good Luck !
TNhunter