Last year I had an onion start to sprout in the cupboard.

Just for the hell of it I suspended it over a glass of water until some
roots developed then planted it out in the garden.

It didn't do at all well - the top growth died off.

However, this year it is growing again and looking quite healthy.

Now, I am assuming that the onion is just another perennial which stores
energy in bulbs and in the wild propogates via seed.
So it may produce a viable bulb after another season's growth.
Is the bulb large each year, or is the first year (grown from seed) or
second year (grown from sets) the optimum time to harvest?

Alternatively it may flower and be just another Alium in the flower bed
without producing much in the way of food.

This could, of course, turn out to be a way of recycling onions which have
been in the cupboard too long :-)

Cheers

Dave R