Cassava grown from an inverted stem cutting is poisonous.

Dr Abe V Rotor

This is not true.  But let us take it this way.  Cassava cuttings if planted reverse 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 roughed, their tubers are now a year old or so. Tubers accumulate poisonous cyanic substances as they mature, so that the longer they stay in the field the higher the poison level is 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. By the way, when preparing cassava, choose the freshly harvested tubers. Completely peel off the bark where the poison is concentrated.  While boiling, take off the pot cover in order to allow the poison to escape as gas.  Cyanogas is similar to the gas used in the gas chambers in executing convicts in the US.  

NOTE: Cassava, also known as yuca, mogo, or manioc - is a staple food for many African families. It is their equivalent of rice in Asia or bread in Europe. Cassava produces the largest amount of food calories per hectare among all food crops, other than sugarcane.This is terrific crop for the region because it requires very little water, can grown in poor soil, and can be harvested year round. Though maize has often overshadowed cassava, the latter is increasingly making its way into the African diet, and that of other regions.