It is necessary... You do it in the winter from about september to march... You can shorten it a bit if you want...
Depends where you live on how you should do it. If you live in the north... ie.Canada, upper states, then if you put it on a basement window ledge, it will still get a photo period, but it will be shorter, and it will be colder so it will seem more natural. If you live somewhere hot, you use thefridge... You only water to keep it undry, not wet though.