It really depends on what types of onions, but yes all onions can grow well in greenhouses. Some onions require certain periods of cold so the greenhouse would have to allow for that (shallots, garlic, and potato onions are all examples).
Yes they onions love sunlight i do to i also love more.
They need full sun, and as much as possible.
5.27hr
Hydrangea require full sun or a good part of the day in the sun.
Lots
The most.
The polar regions never receive any direct sunlight.
Most deserts receive much solar radiation - sunlight.
It does get sun but not as much as mercury and Venus
alot of sun light a year
Most deserts receive 300 or more days of sunlight per year.
none
alot of sun light a year
No, it depends on how you water them and how much sunlight they receive