Light time for germination

We just started our first grow (fingers crossed). I am wondering how long do you leave the lights on for germination? I have read no lights to having the lights on 24/7. What would you recommend? Thank you.

Welcome to ILGM forum. Best place I have found!! :slight_smile:
I believe plants need some dark time to rest so I always use 18/6 for veg. Once the seed has a couple of inches I switch from 24 hours (preventing stretch when seedling first breaks ground) to 18 hrs until flower.
So pretty much from 1 week to flower it is 18 hrs.


Thank you for helping. Just to clarify, Leave the lights on for 24 hours from planting the seed in soil to sprouting. Once the seed sprouts go to 18 hours on and 6 hours off? Thanks again for letting me pick your brain. :slight_smile:

Right. I leave the lights on 24 hours for the first few days the seedling is above the grow medium. Then go to 18. :nerd_face:
You can get the attention of folks here by putting the @ before a user name like @Reticence will give me a heads up. Feel free to ask any time. I am on and off but will try to help where I can. Most everybody here is just the best folks and they know what they are doing.

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@Reticence thanks for the info. Do you use any lights before the seed has sprouted? I just stuck my seeds in the soil today. :slight_smile:

I have my light on 24/7 while waiting for the seeds to sprout, not that they need light at that point but more to keep temps up and stable.


I agree with Hellraiser. I keep the lights on the soil before they come up to prevent stretch. (Not enought light so the seedlings grow fast and too thin). After a few days of growth above ground then 18.


I should have mentioned distance from the light matters the first few days. If you use a CFL keep it within 2-3 inches. Just far enough away to prevent heat damage, but as close as you can. (Again this is to prevent stretch. A common problem with newer folks.)
Forgive me if I am being too simple. Without knowing your experience with MJ or plants in general I am starting at the simplest things.

I’m a beginner and my first germination I didn’t have the lights in and ready… I ended up with quite a bit of stretch… it was easy to fix but keeping the lights on will prevent this issue. Just make sure that there is soil covering the seed. Light can be harmful to the roots.

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Thank you @Reticence and @Hellraiser for the information. I have much to learn, and I grateful there are people like you two. Hopefully, one day I can helps others. :slight_smile:


@Reticence or anyone else, I have a couple questions and hoping you could help. I am also new, and I am planning to germinate Monday. I will follow your lighting guidelines. Will this light be suffice (pic attached)? Also, I plan to do the grow outside, will transplant to larger pot, soil mix etc. in a few weeks, probably mid May. Should I still do 18 hours a day after the first week and until I move outside, even though it will be much less sunlight when they go outside? I read declining light can be detrimental to veg stage, tricking plant to think It should flower? Thanks for any advice, a grateful new member/grower.

I have a T5 light with 4 21" bulbs for germination and cloning.
The light you show will work. Keeo it close to the seedlings. Put you hand under it and check for heat to give you an idea how close you can be without burning your seedlings. CFL lights work well too and are cheaper. Same thing with heat. You can be about 2" above seedlings with a CFL. Only draw back toe the bulb you are showing is the LEDs tend to burn out a few at a time so I would lean towards CFLs unless you can pick up a 24" T5 light. (I didn’t look too hard, but 4 bulb units are about $70).
The end of April this side of the globe has 14+ hours per day. No big deal going from 18/6 to 14 as long as yo are safely past 12/12s.
Happy growing.

Thank you so much for responding! Sounds good. Thanks again.

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