Shrub root stuck in top of downpipe

Crakepottle?

Has anyone any suggestions on how to get rid of or kill a small root lodged in the top of a downpipe? There was a shrub sprouting out of it and I snipped it. There's a lot of moss and strands impacted there. Too high to work on from get above, just reaching my hand up and pulling out bits and pieces. No blockage at all but Im afraid it will keep growing. Maybe there is some weedkiller I could pour down on it and block the clear section for some time to allow it to do its work. Old metal pipe from washbasin in bathroom. Thanks .

10-10-20

If it's cut then it shouldn't grow really, but don't use a weedkiller as it will run-off directly into the groundwater or stream. A blast of bleach on a dry morning, then rinse it off later on that day?

Mr321

White vinegar it'll be dead within 3 days.

10-10-20

https://www.boards.ie/discussion/comment/122533764#Comment_122533764

Safer too.

Gen.Zhukov

If there's an access plate on the side you could use something (drain rods, chimney rods) to push out any debris in it.