The three plants I shared yesterday are a problem in a garden because they self-seed so readily. The plants below don't spread by seeds as much as by their roots, they just relentlessly expand the patch they occupy, overwhelming other plants, and taking over more and more of the garden.
Don't get me wrong, I love our garden, but I feel guilty all the time, because these plants spread more than I can control them. It's not a matter of totally avoiding them, but if you choose to include them, know that you will have to control them. These few plants are a very small part of our garden, which has more hostas and day lilies than anything else. And there are lots of varieties of clematis that are not invasive like the yellow clematis I mentioned yesterday. We have 3 others ourselves, which cause no problems.
There, that's the end of my undergardener rant!