Posted: 17/09/2013 at 09:28
RHS; 'Hormone weedkillers are foliar-acting and translocated, moving down into the weeds’ roots when applied to the foliage.'
Glyphosate is a systemic herbicide
RHS; 'The most effective time for spraying glyphosate is mid- to late summer when the weed has a large surface area.'
RHS link; http://www.rhs.org.uk/media/pdfs/advice/WeedkillersForGardeners