The windows being closed or open makes very little difference unless they are treated with some sort of reflective coating.
A shop light with tube flourescents in it, placed VERY close to the tops of the plants, will solve your problems.
stinkyattic Reviewed by stinkyattic on . stretching question I started about 20 babies inside, when they sprouted I put them all in pots and sat them in my windows. They get a lot of sun, but the windows are closed so its not exactly direct sunlight. I have 7 that are really stretching, the stem is like 3 or 4 inches long on some of 'em, making the stem bend over. What is the problem? I plan on putting them in the ground next week. What can I do, before then, to stop them from stretching so much. Thanks. Rating: 5