Even and successful retting of flax through application of a desiccating herbicide and stand-retting is a major constraint to increasing its incorporation in industrial products. With the release of a new form of glyphosate based on the isopropylamine (IPA) salt with biactivator (Roundup Biactive, Monsanto Ltd), a field trial was planted using three flax varieties with differing levels of ease of desiccation at the Henfacs Research Centre, University of Wales Bangor in 2004. The crop was sprayed at four different times of maturity: mid-point of flowering plus 7 days (MPF + 7), MPF + 14, MPF + 21 or MPF + 28 using two different herbicide treatments; Roundup Biactive (Monsanto PLC) or Roundup Biactive + Restore (40% ammonium sulphate, AmegA Sciences PLC). Fibre quality was assessed following retting and the ease of decortication was measured. The highest fibre yields were obtained from the MPF + 28 spray date, and from the Biactive herbicide treatment. Although lower yields were recorded with the Biactive+Restore treatment, the stems were easier to decorticate. It is suggested that an early sowing date and the use of the IPA salt-based glyphosate with biactivator, and careful monitoring of the crop during the retting process, contributed to the early and successful harvest from the MPF + 28 plots, allowing mature seeds as well as fibre to be harvested from the flax plants.