In article , lid
says...

Not IMO . I'd sever the stems 6" from ground level using longhandled
loppers, then immediately paint or dribble the raw cut surface of the
root end with tree stump killer (from GC), you may need a long spout on
a dedicated watering can, or rig something up with a large milk carton
and hose) . Then fix a plastic bag over each stump (with cable tie) so
the rain won't wash the stuff off before it does the job.

The plants above the cuts will just die anyway so can be left in
place, the holly will soon hide their bare dead stems.

Janet.

I doubt that any systemic weedkiller will have any effect this time of
year. I'd wait until the hawthorn buds show signs of breaking next spring.


http://apps.rhs.org.uk/advicesearch/...d=229#section4

"The best time to apply stump killers is from autumn to winter. Avoid
treatment in spring and early summer when the sap is rising "

Janet.

Interesting. Some manufacturers advise that, others the opposite!

No doubt depends on which chemical their product contains.

I just wonder what happens to stump killer applied in autumn and winter.
Does it somehow soak into the tissues? How does it avoid being washed
out by heavy rain during that period

Just the way I said, above, and the RHS confirmed.

Janet