Seedlings - How much light and when? Too many different answers.

So I started some seedlings on the 8th (11 days ago) and the best of them has it's Cotyledons and two sets of leaves, is about 4" tall.

I'm asking the same question as a million before me, I know... but only because so many have asked and answered, I'm getting too many search results and varying answers. How much light do they need and when? Things I read are saying that they want between 5000-7000k LUX until they have their first set of true leaves, until 16 days, until the first leaves after the cotyledons and a bunch of other conflicting criteria. So far I've given them the 5-8k LUX and they stretched, so I buried them a little and moved the lights down. Now I'm noticing maybe 1 or two with a bit of light bleaching on them but the rest of them seem fine. To my eyes they are perhaps, overall, a lighter color of green than I'd want to see, but they look healthy.

I just want something definitive and agreed upon for when to put them up to Veg light standards. Ideally I'd be using a PAR meter to get the truth out of my veg light, but I don't have the money, so I'm using a LUX meter to measure my LED garage bay light that is growing my seedlings for the moment. Transferring to COBs, waiting for 1 last delayed shipment >.<

Photo of my star pupil. Perhaps just the most Darwinian of them and I'm just clueless.

The stretching and internodal spacing suggest you need more light than you are giving it.

What light are you using?

Lux is what the human eye sees it means almost nothing to plants par is the measure of light for plants.. the spectrum of your garage light isn't right causing them to stretch excessively. I tried my garage light to start seeds and got nothing but stretch no matter how close it was

I have a 2' T12 light I use for seedling, no matter how close I get the light the plants still appear to stretch so I switch to mh right away, slowly moving the light closer and also using the dimmable feature on the ballast. I just use an 18/6 schedule.

9 days under an 8 bulb 2ft T5. They are great lights for seedlings but you have to get them right under it, hence the solos. Replacing bulbs is also key. Light is 2-3 inches away at all times.

I like to use 100W LED bulbs (just regular day light bulbs) at about 1-2" away... or if I have more than a couple of seedlings I'll use my 2' T8 grow light (cheap ass wal-mart thing) or if I have more than 4-5 seedlings I'll use a 4' x 4 bulb T5 light that I use for veg room until flower. Usually I'll move them to the T-5 set up after 3-4 weeks anyway, depending on growth. I'm just a small time med grower trying to keep a legal inventory.

Rule of thumb one out stretched hand should be your futhest point. Start there for a 96watt 4 x 2 or bigger.

The many reasons some are closer or futher could be down to strong soils or environment etc etc.

Average it out youll be good

I'm aware lux is just good for relative intensity and light spread, not actual ppfd.

I'm using a NOMA 4ft, 27W 5000k "daylight" 3000 lumen bar and a "lights of America"? 40W 5000k, 4000 lumen. They are just shy of 6" from top of plants. Providing an average of 11,000 lux. When the sun from the window passes over them they get 100,000 lux for a few hours.

I'll move the lights down really close tomorrow and keep an eye for any immediate signs of stress. Or perhaps just put a booster under a Guinea pig plant and see how it does.before moving the light closer to the rest.

Will dropping my ambient temperature slow their rate of growth? I'm scratching my head trying to figure out how to keep them from getting too much internodal spacing before my cob arrives. Guess I'll just bring in a handful of my 14w LED flood lights lol. Who needs to see at night anyways?

using a hydrodome and two 27W sunblaster t-5’s it still causes stretching at about 7 inches from soil height need to get them about 2-3 inches from the light to avoid stretching. So id say with a garage light you’d want to be just as close assuming its one of those LED T-5 lights. Its really hard to burn the plants with garage lights, florecents or cfls unless they’re essentially touching unless you have some monster of a garage light

edit: I ised the noma light you are talking about for microgreens, i needed to keep it about 2 inches from the top of the soil and it was piss poor (had to use 3 together and the growth rate was abysmal, ended up returning them and replaced the three with a single sunblaster 27W t-5 and get much better results from 4 inches away. I dont think the nomas are on spectrum st all for decent plant growth. They’re litterally the cheapest LEDs cobbled together to produce light. Theres a reason they’re constantly marked down 50-70% at crappy tire

Hadez411 said:

Will dropping my ambient temperature slow their rate of growth? I'm scratching my head trying to figure out how to keep them from getting too much internodal spacing before my cob arrives. Guess I'll just bring in a handful of my 14w LED flood lights lol. Who needs to see at night anyways?

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When it comes to seedlings you want to maintain a soil temperature of 22-24 degrees. Easiest way to achieve this is with a seed matt from your local hardware store. Usually about 30$. I maintain my heat by leaving the lights on for 24/0 until the first set of trueaves show. Not sure if this is 100% proper in regards to the light for cannabis but the majority of plants enjoy full sunlight 24/7 until their true leaves show as plants dont fully start the respiration process until the true leaves have come out, prior to that theyre using another process where most the energy is stored and transferred from the seed instead of the roots or leaves as they arnt fully developed yet. After the true leaves show you want to keep the grow environment temperature between 21 and 26 depending on your humidity. Its also wiite important for seedligs to be wAtered very little and sit in 70-75% RH as it helps during the seedling stage.

Actuosity said:

When it comes to seedlings you want to maintain a soil temperature of 22-24 degrees. Easiest way to achieve this is with a seed matt from your local hardware store. Usually about 30$. I maintain my heat by leaving the lights on for 24/0 until the first set of trueaves show. Not sure if this is 100% proper in regards to the light for cannabis but the majority of plants enjoy full sunlight 24/7 until their true leaves show as plants dont fully start the respiration process until the true leaves have come out, prior to that theyre using another process where most the energy is stored and transferred from the seed instead of the roots or leaves as they arnt fully developed yet. After the true leaves show you want to keep the grow environment temperature between 21 and 26 depending on your humidity. Its also wiite important for seedligs to be wAtered very little and sit in 70-75% RH as it helps during the seedling stage.

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Thank you for the reply and some Canadian shopping experience. I guess I'll try to mainline these and get to ordering more cobs asap.

Hadez411 said:

Thank you for the reply and some Canadian shopping experience. I guess I'll try to mainline these and get to ordering more cobs asap.

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Anytime
Hope to see updates and pics of your grow in the future!

If you have a few CFL's laying around and a socket spliter or two you could make something a bit more powerful than the noma for under 40$.
Two Sockets on long cords with switch = 15$ on Amazon
Two two way splitters = 10.99$ at Canadian tire, or you can get 4 on amazon for 15$)
4 CFL's 27W = 18$ on amazon (can usually find cheaper around but 6500k spectrum i read is best)

For the same cost but less spread of light you can get a single hanging cord for 11.99, the splitters for 15$ and just put two splitters on a splitter and get 4 lights in the same area under the one cord.

The cords are rated for 550W and the splitters 660W, so you'll have no risk of anything with a few CFL's.

You can also often find these items at walmart / crappy tire on clearance carts.
Splitters can commonly be found at value village and pawn shop, if you go to a local electrician or electrical supply shop they often have older ones they no longer sell sitting in the back for cheap of both hanging cables and splitters. (think of those beauties from the 70's and 80's that were shit brown in colour) Like clothes electrical supplies phase out with trends.

CFLS: https://www.amazon.ca/Philips-416016-Twister-Daylight-6500K/dp/B01GA87MZQ/ref=sr_1_fkmr2_2?keywords=philips+27w+cfl&qid=1553084882&s=gateway&sr=8-2-fkmr2

https://www.amazon.ca/JACKYLED-Splitter-Converter-Standard-Adjustable/dp/B07C9HMX91/ref=sr_1_3_sspa?keywords=socket+splitter&qid=1553085102&s=gateway&sr=8-3-spons&th=1

https://www.amazon.ca/Simple-Deluxe-Extension-Hanging-Lantern/dp/B06XCV3CVT/ref=sr_1_14?keywords=edison+socket&qid=1553084969&s=gateway&sr=8-14&th=1

They beauty of using the CFLs for a brief time while youd work on a better lighting solution is they can be used around the house later, splitters are always helpful and the hanging light cords are great for around the garage / digging through the back of closets.

Another nice DIY would be @Way2-High

https://www.rollitup.org/t/super-cheap-closet-setup.982049/page-4

Example of cfl: this one is 216W and cost about 57$, though it wasnt meant for cannabis it was originally just meant for normaly vegitables just had a cannabis plant die on me so I repurposed it while I wait on tax refurn for a CMH system.

The reflector is made from two pieces of cardboard to hold it around the socket, folded aluminum about 1.50$ worth and the edges are made from the aluminum rolls cardboard center which allows you to bend it gently and maintain its shape.

Actuosity said:

Example of cfl: this one is 216W and cost about 57$, though it wasnt meant for cannabis it was originally just meant for normaly vegitables just had a cannabis plant die on me so I repurposed it while I wait on tax refurn for a CMH system.

The reflector is made from two pieces of cardboard to hold it around the socket, folded aluminum about 1.50$ worth and the edges are made from the aluminum rolls cardboard center which allows you to bend it gently and maintain its shape.


View attachment 4303571

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I would just have gotten a long power strip and some bulb to wall outlet adapters... you really over-engineered this thing.

I put the lights within inches and repotted a few. Readings were 19k+ lux One immediately stretched up again, but others didn't. Here's a picture of the leafiest one and the thickest stem one The thick stem one has more roots hands down, but less foliage..

Actuosity said:

Anytime
Hope to see updates and pics of your grow in the future!

If you have a few CFL's laying around and a socket spliter or two you could make something a bit more powerful than the noma for under 40$.
Two Sockets on long cords with switch = 15$ on Amazon
Two two way splitters = 10.99$ at Canadian tire, or you can get 4 on amazon for 15$)
4 CFL's 27W = 18$ on amazon (can usually find cheaper around but 6500k spectrum i read is best)

For the same cost but less spread of light you can get a single hanging cord for 11.99, the splitters for 15$ and just put two splitters on a splitter and get 4 lights in the same area under the one cord.

The cords are rated for 550W and the splitters 660W, so you'll have no risk of anything with a few CFL's.

You can also often find these items at walmart / crappy tire on clearance carts.
Splitters can commonly be found at value village and pawn shop, if you go to a local electrician or electrical supply shop they often have older ones they no longer sell sitting in the back for cheap of both hanging cables and splitters. (think of those beauties from the 70's and 80's that were shit brown in colour) Like clothes electrical supplies phase out with trends.

CFLS: https://www.amazon.ca/Philips-416016-Twister-Daylight-6500K/dp/B01GA87MZQ/ref=sr_1_fkmr2_2?keywords=philips+27w+cfl&qid=1553084882&s=gateway&sr=8-2-fkmr2

https://www.amazon.ca/JACKYLED-Splitter-Converter-Standard-Adjustable/dp/B07C9HMX91/ref=sr_1_3_sspa?keywords=socket+splitter&qid=1553085102&s=gateway&sr=8-3-spons&th=1

https://www.amazon.ca/Simple-Deluxe-Extension-Hanging-Lantern/dp/B06XCV3CVT/ref=sr_1_14?keywords=edison+socket&qid=1553084969&s=gateway&sr=8-14&th=1

They beauty of using the CFLs for a brief time while youd work on a better lighting solution is they can be used around the house later, splitters are always helpful and the hanging light cords are great for around the garage / digging through the back of closets.

Another nice DIY would be @Way2-High

https://www.rollitup.org/t/super-cheap-closet-setup.982049/page-4

Click to expand...

Thank you for the in depth reply. Did use some cfls I had laying around for a bit, but they were kinda crappy and half the usual size.

The marijuana God's must have been smiling at me this week. I came up with the cash to get 240W of bridgelux cobs. Should be enough to grow two good or three OK plants perhaps.

3rd Monkey said:

9 days under an 8 bulb 2ft T5. They are great lights for seedlings but you have to get them right under it, hence the solos. Replacing bulbs is also key. Light is 2-3 inches away at all times.

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12-13 days

Actuosity said:

Example of cfl: this one is 216W and cost about 57$, though it wasnt meant for cannabis it was originally just meant for normaly vegitables just had a cannabis plant die on me so I repurposed it while I wait on tax refurn for a CMH system.

The reflector is made from two pieces of cardboard to hold it around the socket, folded aluminum about 1.50$ worth and the edges are made from the aluminum rolls cardboard center which allows you to bend it gently and maintain its shape.


View attachment 4303571

Click to expand...

to help take off the tin foil ........it is doing more damage then good the the foil reflects and retains the heat ( cold grows ok but anything above 60F it isbad idea)
look into something called IR blocker..........yes it does reflect heat but the patternes in it defuses the light in a useable way