Vegging, How long is too long?

Right now I have 4 clones that are about 6 inches tall, under a 400 watt MH bulb in rockwool. I've been running them for 16 hours on, and 8 off. Am I leaving my light on too long?

I veg at 18 on 6 off. Some veg 24 on. I feel plants need some recover time in the dark.

Mine really took off when I changed from 24 to 18/6.

I think I'm gonna do that tonight. thanks guys, what do you cut the light to when its budding?

Mohican said:

Mine really took off when I changed from 24 to 18/6.

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Really? Are you sure it was the light change? Could it have been something like being later in the plants life or more nutrients? That is interesting. I run mine 24/0 and have heard many differing opinions. I may do one grow at 18/6 and change nothing else just to see what happens. If it is the same or more growth then I would love that because its cheaper! Sorry, that's my Jewish side, always trying to save money.

Darthbudz said:

I think I'm gonna do that tonight. thanks guys, what do you cut the light to when its budding?

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12/12 and wait for the goodness!

EDIT: you actually need to set the light to 12/12 to induce flowering, or else it won't happen (unless you have an autoflower strain).

12/12 and some people go 16/8, 15/9, 14/10, 13/11, 12/12. This gives the plant some time to adjust.

someone advised me to cut it back to 8 hours for budding/flowering, what difference do you think that would make

anything lower then 12/12 will induce flowering the only advantage i see in cutting it to 8 is to try and flower a bit quicker and this may promote more trichs but this is just my theory no fact behind this

Mohican said:

Mine really took off when I changed from 24 to 18/6.

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this is a common misconception. whats you forget to account for is that plants grow exponentially fast. so the plant would seem to be growing faster but its because of the natural exponential growth. if you did the experiment backwards you would conclude that 24 hour lighting grows plants faster. 24 hours and 18/6 will produce the same plants. The only real difference will be what happens to the equipment. The switching of bulbs off and on is what will lead to them blowing out. I'm sure you've noticed the light bulb always pops immediately when you flick the switch on. for instance, replacing t5 bulbs is more expensive than the extra energy it costs to run them 24 hours. HID's however run so hot they should have a chance to cool down as well as the ballast. HID bulbs are so well made these days you can switch them on and off so many time that you'll replace your bulb from lumen degradation before it ever pops on you.