Is there a trick to grow green onions?

stick the root ends from a shop bunch in a glass with an inch of water on the windowsill, change the water every couple of days, cut what you need. that's the renting version and it holds up for three or four cycles before they go thin. for proper ones, a pot of compost, same root ends or seed an inch deep, water when the top dries out. the two guides disagree because one is about seed and one is about regrowing. both work.