" writes
My guess is that this is not a different ivy but just the explosion of
growth of the original ivy, lighter green because it is growing fast to
cover ground.

I'm surprised to hear that. I think it is a different type. We have
had only the tiny three-forked dark green leaf type for the last 17
years and the new stuff is a quite new, although next door had it last
year, and it has run amok over the side of their house and outhouse.
The leaves are long eye-shaped and lighter green, and it stands up
from the surface and waves in the breeze.

Well, you're on the scene and in a far better position to decide than I
am. If you're sure it is different, then you can go ahead and glyphosate
it without fear of killing the original.
--
Kay