"Boron-toxicity symptoms were not observed on rapeseed plants at the highest level of boron application. Rapeseed is a heavy feeder of boron; further, it does not have the sensitivity that many other crops have to excessive amounts of this nutrient." 1
1- Wooding, F. "Interior Alaska Crops Respond to Boron Applications", Agroborealis Vol. 17, No. 1 1985 p. 47.