Plot-holders are permitted to use weedkillers such as glyphosate (often sold under the trade name Roundup), particularly when clearing a new plot of perennial weeds.
However, please be aware that many of our plot-holders garden organically. Only spray on a day with little or no wind, and when there is no forecast of rain. Be considerate about using chemicals close to another person’s plot: if tackling a weed that goes right up to a neighbouring plot, discuss with the plot-holder first before spraying.