I'm starting to grow indoors, but I can't allow my plants to grow too high. How do I make sure they stay under 1.5-2 feet tall without killing the plant?

do a search for low stress training or scrog(screen of green)
also remember that the plant will want to double in height when flowering, so you can assure a low stature by flowering when the plant is only a foot tall or less. the problem with that will be yield.
bigger plants=more budz

top em...tie em down

you can find plenty of information on these methods in the FAQ

you will want to plant a more than ordinary the average amount of babies seeing how you won't allow much growth vertically

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