Originally Posted by SwampYankee

A lot will depend on how fast the weed is actively growing, here in southern New England (still in the 40's, cold rain) plants aren't doing much of anything right now. The glyphosate is carried through the plant's leaves to the roots so if there isn't much translocation going in, it'll take a long time for the chemical to get there.

Roundup (glyphosate) will take about 5-7 days to show visible signs even though it starts working within a day or so. Roundup Plus or Roundup Pro (glyphosate + diquat) will show "death" within 2-3 days even though the total kill will take the same amound of time as straight glyphosate. All of that assumes ideal growing conditions.