[zephrindruin]

New allotment glyphosated, now praying it doesn't rain. We have noticed quite a few clumps of spikey marram type grass. Does glyphosate work on that type of plant? Also does this indicate that the soil is acidic?

[Salmo]

My guess, without seeing it, is that your clumps are cocksfoot. Yes it does if you have applied it while there is green growth.