Don Smith wrote:
Thanks Ian for your help.
This patch of weeds must be particularly persistent.
I'll make up another brew, add some washing up liquid and get to it.
Don

One of the mistakes people make with this stuff is to prepare too strong
a mixture. Follow the instructions on the bottle when preparing the
mixture. Plants are not stupid. If they feel that the mixture is too far
away from what rain would normally feel, they consider what they are
being sprayed with as harmful to them and put into action their normal
defences by closing the stomates.

Cheers.