When to change from 24-hr light to 18, to 12

Two White-Widow feminized seedlings in 5-gallon growbags with compost, perlite, coir mixture. Pics below. I started the seeds in those little peat pots with netting around them, then put those into the grow bags after a week or so.

I have the lights with vegetative bulbs, on for 24 hours now.

1: When should I change from 24 hours on to 18 on / 6 off?

2: Do I wait for flowering to change to flowering-specific bulbs (which I have)? At that time do I go to 12-12?

Thanks in advance!


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The only time I do 24 hour lighting is when I’m revegging a plant. Otherwise it’s 14/10 for veg (I was doing 18/6 but decided it wasn’t necessary) and 12/12 for flower.

As for when to switch to flower, I have started 1 month old clones and have waited until 10 weeks of veg. A good rule of thumb is to leave the plant in veg until it’s using about half of your growing area. They have the potential to almost double in size during flower.

First day at 12/12

Two weeks. Notice I had to put in a second net?

4 weeks.

8 weeks


Thanks, I will change the timer now. I’m not doing SOG or SCROG, just being lazy. This first year for me is basically about experimentation and having fun. I have a bunch of plants outside in grow bags (White Widow and Granddaddy Purple not yet flowering) and raised beds (Lowryder auto and Wedding Cake auto which are almost ready to harvest).

So these new basement plants are just another way to enjoy the gardening hobby.


If you’re looking to experiment, try using a DWC or rDWC setup. I know it’s not soil, but results can drastically increase. I went from producing 560 g in my 1-1/2 m/sq area to 1032 g in the same area and now with a little tweaking I’m pushing close to 1250+.

I run a half/half system. A rDWC mixed with fogponics.

Here is a pic from 3 weeks ago, they are in all different stages of growth. Pardon the mess, working on defoliation at the time, also working on expansion so stuff is getting moved around.

What do those acronyms mean?

DWC (deep water culture) and rDWC ( reservoir deep water culture). You run a fish aquarium air pump with 4”x2” airstone in a bucket mostly full of nutrient rich water, to produce steady airflow to your root system.

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