Im new to growing, my first plant is 3 weeks along and getting its second pair of the full finger leaves. When does a plant enter its vegetative state? How long should i let it grow before i do the 12/12 stuff? thanks for the advise
You can probably put it into flower if you'd like, but your yield won't be much. If you veg a plant for at least 4-6 weeks so it grows a little before flowering it, you'll yield more.
Since you're working indoors, you control when you flower your plant. I advise letting your plant get about 2/5 of the way to your maximum height and then flower. That way you have plenty of room for your plant since they double in size during flowering. Sometimes they grow more than double the size though so just maintain a good height and you're good!