Sabaa Mundia wrote:

hi,
i bought a bag of onions from the supermarket and kept it in my garage,
after a few days i took out an onion that had grown yellow shoots, i put it
in a container containing water. after two days the shoots have have become
nice and green.
i want to know that if plant it will i get onions growin underground or
what will happen.
thank u
sabaa

They'll grow into bigger onions.

Onions are heavy feeders. Give them 10-10-10 or diluted 20-20-20
every couple of weeks. Harvest the bulbs when they "trip," i.e. when
the tops die down. Harvest the tops for soup any time you like.