Cut the problem root off down low in the hole and then cover it up.

First of all...WOW - 1b, never met/emailed anyone from there. That part of the world would give you some gardening headaches, I would imagine!

Anyway, I agree with bboy. Cut out as much as you can or maybe even try watering well to loosen up the soil and then commence to gettin that root all the way out. Roses can regenerate from a small piece of root, but I'm not so sure about Cotoneasters. They might be wimps and you've killed it already!

If it does pop up, paint IT with Glyphosphate ( Roundup ) and that will kill it off.

Good luck, I think you'll be fine.

Conon, I use the Canadian zone map, I'm not sure what the equivalent US zone is, probably 2. I'm in northern Manitoba. I can tell you that cotoneaster is very hardy for this area, but seems to be very disease prone. I'm glad to get rid of it.
I did work harder at removing more of the roots and feel more confident now.
Thank you both for responding. It helped.

you are comparing apples with oranges ....

wild roses are invasive.. and will resprout from the roots ... because they can bud underground ...

trees do not have dormant buds at depth ... and odds are about 99% that it will not respout from down there...

if you wish.. paint some round up on the severed root.. let it dry.. and then just replant above .... it will not affect whatever is planted above it ..

ken

Ken, I was hoping that that was the case. As I was working so hard, it occurred to me that it wasn't necessary to dig out all the root, so I posted the question. Incidentally, it wasn't a wild rose, but one that annoyed me by dieing back to the ground every winter. But in any case, the dogwood is planted now and ready for the weekend's predicted rain.

I removed a huge cotoneaster several years ago and it didn't resprout even though I had to leave a lot of root.

Glad to hear that, Laceyvail.