Which plant demands special processing to make its flour non-poisonous for people?

in some countries, bitter cassava water was a traditional means of wives murdering husbands long ago.

One of my favourite vegetables...

Wait, so I can die if I eat it?!?

Player #11549463, no please. sago comes from a palm I believe

best to avoid the "Cyanide [...] formed following the hydrolysis of cyanogenic glycosides that occur during crushing of the edible plant material either during consumption or [...] processing" -- IntechOpen