Light Cycle/Flowering Question

I've been lurking here a few days and have found some really great answers here. I'm posting for the first time as a specific problem as arisen with my grow.

I live in northern usa so the winters are pretty cold. Currently I have a 4 plant grow that I'm rather certain are ready to flower. I beginning to see sex parts and they're still on an 18/6 cycle.

They're in an uninsulated attic. Temperatures getting too low is a problem. My 400w MH currently runs on from 8:30AM to 2:30AM and off in between. The lamp is a great source of heat and will keep my plants at the proper level (supplemented with a space heater).

My problem is this; I'd like the light to be ON at night, and off during the day. The ideal thing would be ON at 8:30PM and OFF at 8:30AM...leaving the lamp on at night to heat the plants.

My lamps been on since 8:30am it is now 8:55pm of this post. They light is set to go off in about 5.5 hours. Can I just leave the light on until 8:30am then switch it off to achieve the desired 12/12 day/night cycle?

I'm basically asking if going 24 hours then switching off for 12 to begin the flower cycle would damage the plants.

Yes, you'll be fine. Many people use a 24/0 veg light cycle anyways, so it shouldn't bother the plants one bit. Plus, they can typically take more abuse from light schedules in veg than they can in flowering. If you are still uneasy about doing it that way, simply get yourself a timer and every two days or so, set it back (or forward) an hour and after a week or two, you'll be ready to flip to 12/12.

It won't hurt them at all. In fact it's said that giving them a 24hr dark period before switching to flowering helps them show sex faster. I can't say for fact that it's true, however, I've done it myself, the plants were not harmed, and they showed sex four or five days after the switch. I would still be concerned about the cold though. Right now in my house with outside temps dropping, the temps range from 65-75 on average (lights off and on). But in your growspace it may be colder than that. It will definately be too cold before they are done flowering, you'll have to find a way to get some heat to them.

Just saw you said you have a space heater on them, good deal - you should be fine then.

Thanks for the replies. When the timer was set to go off at 2:30AM i just let it stay on until 8:30AM. So they had 24 hours of straight light before they went to 12/12 but they look fine. That and the light DEFINITELY helped regulate the temperature at night.

Thanks for the help guys. I've made quite a few noob mistakes on this grow (it is my first even quasi-real grow) but I've learned about as much as I have from all the books I read. This sit helps so much as well.

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