In article ,
Mick wrote:

It is in what amounts to a big brick built pot, around 25 feet long by
6 feet wide and 3 feet deep, but when it was built in the 80s they put
clay in the bottom.

I can get bits of root out until I get to the clay, and it is filled
with plants now too.

That's ample deep enough - it's doesn't regrow well from deep
roots (unlike bindweed) - but the plants are an issue. I would
use glyphosate, but I really do mean half strength.


Regards,
Nick Maclaren.