But now techniques have been developed to isolate THC, the narcotic element of the plant, so that "safe" varieties can be licensed and grown without the danger of hemp pesto being merely a cover for trade in "whacky baccy". The upper limit for THC content in Britain is 0.03 per cent and MotherHemp's plants contain less than 0.01 per cent. This is in the flowering heads, all of which are cut off and left to rot in the fields.