ok, i put the lil baby about 8 " from the light, i'll move it closer when it stretches?
as far as when to harvest....there are some guides on the rollitup.org faqs you should read.
https://www.rollitup.org/view.php?pg=faq&cmd=category&id=59
But...... here is harvesting time short and simple....quoting from...
http://www.a1b2c3.com/drugs/mjgrow9c.htm
"The optimal time to harvest marijuana plants is when THC production has reached its maximum. A rough guide as to when to harvest is to wait until 50%-80% of the white pistils (hairs) have turned dark (usually brown or red). But a better method of determining when to harvest is to wait until certain trichomes on the plant have matured."
"The best time to harvest a marijuana plant is when a majority of the trichomes have turned to a milky translucent color. See
these images of what trichomes look like and what color they should be at harvest time. Not all the trichomes will mature at the exact same time, so harvest when most of the plants are ready." --- to use this method you would need at least 30x magnification to look at the trichs
Be sure you read proper drying and curing techniques on the FAQs as well.
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Let your seedling get a couple inches tall (at least) before you start to give it full light (and no nutes for a week or two). I don't push plants into full veg (high light and full nutes) until 3 or 4 sets of true leaves form (when rapid growth starts on the plant...and it's probably 5 inches tall or so....). good luck!