I would goto Home Depot or Lowes, and buy you a cheap timer and set the lights up for a minium of 12 hours and a maxium of 16 hours. right now i have 20 indoor plants and 10 flats started of differnt things and i have my lights set at 16 hours and I am seeing awesome results. You may also need to play with the amount and longegivity to your specific needs.

Thanks , I was thinking they where getting to much light..

16 on/8 off. It is the dark time when they do their growth thing using the energy stored while the lights were on. ;)

I agree 16 on 8 off, plants need there down time.

My rose cuttings are on 24/7. The growth is phenomenal, don't believe when people say the plant grows when it's dark. I can see it growing from when I check in the morning, and when I come back from work, to when I get up the next day. Everything is growing great, stem, leaves, roots and flowers.
Some plants need a COOLING OFF TIME, if the temp is a little high, and some studies show that fluctuating the temperature is of benefit, and the same studies show maximum growth occurs on 24/7. I can't find Henry Kuska's post on the subject, but he did confirm this, and as you all should know, he is a seriously experienced grower. You might be able to find his post by searching under his name in this forum. Paul Mozarowski.

plants dont just grow when its dark. they are burning up there stored energy but it does not mean that is when they are growing. what about when it stays daylight for months in alaska? at that time they have massive amounts of growth.

If you'd like to learn more about the two stages of photosynthesis - Light Reactions and Dark Reactions - and the resulting plant growth, check out the article linked below.

Dave

Here is a link that might be useful: Photosynthesis and Plant Growth

Like the article says, the dark reaction is a misnomer, it doesn't require dark, it is just independent of the light and will occur in both light and dark. Dark is not necessary or required for photosynthesis, but light is necessary and required. The bottom line is that the light reaction can only occur in the light, and the dark occurs in both light and dark, so that's why I keep my lights on continuous, because light and dark reaction takes place at the same time all the time, and the light reaction cannot occur at night, just the dark reaction. so 24/7 Paul Mozarowski.