Cassava grown from inverted cutting is poisonous.

Dr Abe V Rotor

This is not true.  But let us take it this way.  Cassava cuttings if planted upside down will take a much longer time to grow, if at all. Those that survive become stunted (bansot), thus at harvest time they are left behind in the field. Come next planting season, and they are rouged, their tubers by now are about a year old. Tubers accumulate poisonous cyanic substances as they mature, and the longer they stay in the field the higher is the poison level in their tubers.

A one-year old cassava tuber has twice the amount of cyanide than regularly harvested ones do (4 to 5 months in the field). Thus cassava poisoning is not uncommon. Beware of cassava tubers harvested from borders or along fences. These must be very old indeed. By the way, when preparing cassava, choose the freshly harvested tubers. It is in the bark where the poison is concentrated so that it should be completely peeled off.  While boiling, take off the pot cover in order to allow the poison to escape as gas -  cyanogas , which is similar to the poisonous gas used in executing convicts in the US.  ~