Will Triclopyr kill trees bushes under treated Creeping Bellflower

[JustMe23]

I am battling the invasive species, Creeping Bellflower. Not realizing what the pretty purple flowering plant was for too long, it invaded much of my landscaping and needs to be eradicated. Bellflower is under many mature bushes such as Montgomery pines, CO Blue Spruce, Lilac, Cottoneaster, etc. Due to the mature size of the bushes, I am not able to get under them to dig it out as they are close to the ground, and it's too prolific for digging to be effective.
I have researched to find that presently the belief is that Triclopyr is the most effective herbicide, available to homeowners, to kill Creeping Bellflower. Repeated applications will be necessary.
My concern is that although I do not plan to spray Triclopyr, but rather "paint" it on each leaf (ugh, what an arduous project!) I am concerned the herbicide may reach the roots of the bushes/plants below and kill them off as well, after eventual rain, watering of surrounding plants, or dripping from the leaves to the soil after application. I very much will appreciate your expertise and advise on killing the Creeping Bellflower but not the roots of the bushes growing beneath it.