On 05/01/2016 14:20, Nick Maclaren wrote:

Does anyone know how long it takes to work at this time of year?
My guess is 1-2 months, but i could be wildly wrong.

In a normal cold year it tends not to work at all in winter.

This year with some weeds still in active growth and flowering I expect
3-4 weeks to show some yellowing although I haven't tried it myself.

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Regards,
Martin Brown