well.. first.. its obvious you cant kill them ... lol .. what i define as a shrub you could run over with the truck .. lol ...

it doesnt sound like you have the variety that is going to stay at 6 to 8 feet ... but with enough hard work.. you might train it to that height .... but personally i dont like to work that hard.. multiple times per year ....

so dig in.. or abandon them .. the best thing i ever did at my first house.. was to get rid of every mistake the prior owners made ... unfortunately.. it took me 10 years of hard labor to come to that decision...

also.. yes.. thin them out.. you do not need to pamper every new shoot ... remove half of them .... properly ... at the trunk.. if you leave any stub.. you will most likely get a million more shoots ...

your base problem.. is that you have a mature root mass on a baby plant.. obviously it has the ability to produce the nutrients for EXPLOSIVE!!!! growth .... is that an understatement.. lol ... and these things are going to be aggressive forever ...

if you have a couple.. try differing methods on each plant.. and see where that gets you in a few years ... you can always cut them down again.. and start over.. if a preferred method is decided upon ....

and also.. remove some.. starting new problems [for the next owner.. lol] ... so that by the time they start getting bigger.. more of the other can be removed... if you so wish ..

good luck

ken

I had one of these at our old house. To keep it 6'-8' tall will be alot of pruning, and it won't look graceful.
If you prune an upright branch at 6', it will sprout new branches close to the cut at a 90 deg. angle from the cut branch - looks like a very bad haircut.
My bush liked to grow up and arching like a fountain.
I let mine get as tall as it wanted - over 18' - but cut branches out from the base to narrow it, and then trimmed side twigs as needed. It eventually formed a tunnel to walk under, and when in bloom it was beautiful.
But it required alot of trimming, at least twice a year, and we still got poked in the face alot when walking past / under it.
I thought it was worth all the effort! (But I was alot younger back then...)

Thanks for your reply. I'm not sure what to do. The bases of these two plants are at most 6 feet from where I need our front path to go. I don't mind the height so much as the width... and it sounds like I might be fighting a losing battle to try to keep them less than 12 feet wide, huh?

And sadly it's not like I can just dig these guys and replant elsewhere: as mentioned the bases are enormous. One of them is actually even bigger around than I'd thought (now that the snow has melted) - probably 42-48" across and thick with hundreds of shoots. Honestly I don't even know if I'd be able to dig it all out by hand, even if I'm not trying to save the plant!!

I will have to go out there this weekend and rethink things I guess. Anyway, thanks for chiming in with your experience.

I kept mine to maybe 5 main branches, the biggest was 3" diam., & trimmed off the lower small branches so I could plant alot of stuff underneath & expose the bark. The wood isn't too hard, so it's easy to cut if the diam is kept manageable. If you trim a side twig all the way back tight to the main branch, most likely it won't sprout at the cut. And the sprouts from the base are soft & easily cut w/ pruners.
If it was my shrub, I'd select a 12" area to keep; cut the rest of the area to ground level & cover w/ heavy black plastic, big rocks & mulch, & see what happens. I think these roots go straight down deep - rarely needed supplemental watering. Digging it out could be quite difficult.
I'd guess my shrub was 30 years old & the base was only 12" diameter, but it was planted in dry east exposure shade - which probally slowed the spread.
It was on the side of our house, arching over the gate into the backyard. The base was 36" from a sidewalk. Between trimmings or when in bloom we'd just duck to avoid getting poked in the eye.
I can imagine a front path main entrance location could have been a problem.
When in bloom, it would get so heavy w/ all the tiny flowers, the branches would weigh down halfway to the ground. After it bloomed, and all the tiny flowers started to drop, it would look like it was snowing. The layer of fallen flowers was so thick on the ground you couldn't see the sidewalk.
It's a bush worth trying to keep!

Thanks so much for your input. I'm going to try your suggestions this summer and see what happens... I really appreciate it!