Suckers on my Sorbus Sargentiana

I have demolished a massive Herbaceous border and will be turning the area into grass if it ever starts raining again! In the area are 3 reasonably established Sorbus Sargentiana that I planted about 15 years ago. 2 of them have annoying suckers of what I am pretty certain is the common Sorbus which has been used as a root stock.
We all know that pruning the suckers makes the situation worse! To get the ground level enough to be able to cut the grass when sown I need to do something about the suckers. Can I weed kill them or will the weedkiller translocate into the trees. I seriously do not want to kill them as they are beautiful. Alternatively I could try and dig up some of the shallower roots but again how many are safe to dig up and thus could be extremely hard work! Not sure how best to tackle the issue other than allow a “ circle round the trees” and not seed it but that is a bit of a faff. Hope someone has some bright suggestions.

 

Not sure.
I use glyphosate on Tetrapanax suckers and seems to have no affect on the main plant, and pretty much not on the suckers for long to be honest.

 

You are supposed to pull off suckers as they are then less likely to shoot; so I'd pull off the ones I could. If you only have a couple left after pulling the rest of I'd dig down cut the root they are coming off and then remove them.

 

I always think the old advice of pulling off suckers was written by some Victorian "gardener" who had staff.

In my experience they usually just snap off and rarely come away cleanly from the root.

They usually appear where roots get damaged by cultivation around the root system.

 

Thanks, unfortunately you would have to be Charles Atlas to pull these sucker off. They are substantial. I am going to give weed killing some an go and see what happens. Funny how 2 of the 3 Sorbus have them and the other not one. Wish all 3 were suckerless!