How Long Should Your Grow Lights Be ON Each Day For Best Results

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[Nancy-zkdj]

Instead of lowering my lights, I raise the flats. Some flats grow different under the same light, so I can lower a flat as they grow. Many things can be used under the flats, small boxes, old cake or muffin pans...works for me!
Great information on the time, thank you! ❤

[dadmezz]

Thanks Luke.
Your timing works for me.
My setup has four wire shelving with four single strip meds of 5000 Lumina each.set to highest length.
I use silver reflective sheet film around the shelving which magnifies the brightness.
Works great for this small back yard gardener.
The wrapping also acts as a small green house elevating room temperature slightly to assist growth.
Love learning to grow from seed, so over plant and gives extras to family, friends and neighbors.
It is a good bonding event we can all smile about.
Thank you Luke for your info so I can bring joy in my own way..

[kevinlpilling]

I hang those reflective emergency sheets around the grow light area. The light is reflected back and forth, plants grow strong and don't lean. Can get at any dollar store for a buck.

[L_i_g_h_t]

I'm really grateful for you, Luke. My main problem with most gardening resources is that they assume we know some basics that I personally did not know, as someone who was basically never around any gardeners but really wanted to learn. You're really great at explaining in layperson's terms all the little hows and whys that those other resources don't. The "whys" also make it easier to remember what you teach us. So, many thanks. :)

[katjoy]

Great comments. Lighting is often experimenting…taking things slowly…watching how your plants react.

[j.d.preppingerie]

I am on the Michigan- ohio line, and have been learning more about seed planting indoors every year. I built my first greenhouse two years ago, last year built a larger one and transplanted my plants into the greenhouse when I think it is safe from frost. Before that I had always bought all my plants and it was over 200.$ I new I had to do something different.

[austin]

I'm growing kale indoors this winter. 12 hour on/off cycle under a 4 foot shop light is working out very well.

[haroldgreen]

Always good to find out what works for other people. My indoor plants are in a grow tent. I have two 600 watt, marine full spectrum led lights. I like them because I can grow with all blue/white leds and not get the too much light leaf burns. I try to keep the lights around 4" to 6" above the plant tops. I set my timer for 16 hours on to grow plants that are short and very dense. When I want blooms I shorten the day length to 12 hours per day. The inside of the grow tent reflects the light to the lower leaves to keep them full. Now out in my old greenhouse the plastic is not really letting in the full intensity I need for vegetables so I hung some cheap four foot led shop lights. They are a couple of feet above the plants but they are just there to add to the natural light levels from the sun. They are on a 12 hour on schedule. They've increased grow speed by close to 100%.

[davesterchele]

Side reflectors do make a big difference. Plants in a reflective wall grow tent will get more light across the length of the plant vs. just shining straight down.
also consider turning your plants from time to time and adding/removing stands to move your plants closer/further away from the lights as needed.

[mikemiller]

There's lots of variables when growing indoors.. if your plants are growing tall and spindly chances are your lites are too far away, if the top of the plant is curling up and dying the lite is probably too close, a fan running on the plants help hardening off seedlings and is a good idea to run all the time, , Nice post Luke!

[michaeldossett]

One thing to mention is that some long day plants shouldn't get more than about 12 hours even if they are further from the lights - the solution there is adding more light rather than longer so as not to trigger bolting or other physiological processes prematurely. Two things that this is especially important for are spinach and onions.

[craighalle]

Luke it's very pleasing that you answered one of the questions I had about grow lights. I remember telling you what happened to me and how I fixed it. I had 2 tiny Roma tomatoes that I never transplanted. So I rolled the dice and transplanted them under my grow light. They are growing like crazy. I win! They may mature before I get them outside this spring, but I will enjoy watching them keep growing on. Another excellent video Luke. May the Lord keep blessing you and yours. Love you buddy.

[shauneilscott]

Like all things gardening, pay attention to the plant. I just lost my avocado to over "enthusiatic" fertilizing because well the soil was "depleted." I am praying it forgives me and returns after being moved and pruned...I should have just enjoyed how happy it was and ignored all of the "instructions." Oh well...

[DotTrotsLowCarbLiving]

How does this impact onion seedlings? Should I plan to stay below their hours needed to begin bulb formation?

[hossenfeffer]

Since controlling all the variables I.e. light distance from plant, light output of bulb, light needs of individual seedling varieties, reflective qualities of walls, humidity of the grow room, even temperature of grow room — may be difficult for gardeners to control, I appreciate your comments on observing how the plants are doing, what the signs are of light deprivation, etc. This is going to be the only way most of us can judge how our seedlings are doing, so your experience with observing the expected growing habit of a plant and how to judge when something is going awry will be most appreciated. This does all come with experience, reading, vids, but it really takes, I think, 3-4 growing seasons to figure out the basics for your own plot. Or a grandfather to advise you. 🇨🇦

[jackicarroll]

I have a KlimaGro (probably one of the last made) indoor greenhouse unit. I have always struggled with how high to set my glass shelf and have added extra grow lights beneath the glass shelf etc. Your comment about lighting is often experimenting is very true in my case and watching this video has given me more insight to be able to tweak it a little bit more as far as the time I am leaving the lights on for my seedlings. I wasn’t leaving it on nearly as long as you suggest for tomatoes and they seemed to grow fairly slow. Thanks for the fresh information.

[madammazon]

Thanks Luke! I've watched past videos and it's always nice to get a refresher right before I need to do seedlings again!
Don't give in to the pressure to give a hard number! Stay strong! You give us knowledge and that gives us power - we can take any light from anything and apply it! Thanks!😆

[PorchGardeningWithPassion]

I am glad you mentioned plants in Alaska regarding time with light on them. I have been running my grow lights 24 hours at a time for my leaf lettuce to see how things go and so far the results have been awesome! I have been adding some dead periods of a few hours here and there to not overwhelm my Oregano plants that are super tiny that I want/need to do well.

[kburkes]

Good info. I also like to use mylar blankets around my grow racks to reflect the light back onto my seedlings. Seems to help keep them warm, too.

[JSJTOUTDOORS]

When my seeds first germinate I star them at a 16-8 for light/dark . Once they get established about 2 weeks after germination I bring them down to around a 12-12 or to resemble more of a spring day in Indiana. Around the 4th week I also introduce a fan onto the plants to get them good air flow since they start to get a little crowded and get them to become more sturdy by trying to stabilize themselves from what they think is the wind trying to blow them over. I feel as if while the fan drys them out faster it also prevents mildew from starting and forces the plants to take up the water faster before the fan takes the moisture away.