How much light do seedlings need?
- Thread starter Afghan_Landrace
- Start date
MickFoster
Well-Known Member
Some people do 24/0........I prefer 18/6........both work.
Herb & Suds
Well-Known Member
It looks good what wattage?
Afghan_Landrace
Member
I'm just winging it I have no idea what I am doing. I got a T5 (8W) and a two of those blue and red LED lights 5W each. Before these I was using a CFL 12W and a tiny Red/Blue led bulb not sure of it's wattage
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LeastExpectedGrower
Well-Known Member
I usually do 18/6 with ~300 PPFD. I also use a mild/indirect fan on 'em to start building up the stem a bit so you don't get super thin/stretchy.
Afghan_Landrace
Member
Yes I have ordered a tiny fan for that same purpose. Over the weekend I moved the cup out under the sun. Otherwise it stays under these lights.
LeastExpectedGrower
Well-Known Member
Sun can get really strong really quickly, so be careful with new plants. There's a bunch of good hardening off procedures to get them not to burn under sunlight.
Afghan_Landrace
Member
I worry I'm not providing enough light so I thought it might be good for it. Also, I might have to eventually move it out if it out grows my grow space, so I read a bit of conditioning is good for it.
LeastExpectedGrower
Well-Known Member
Download one of the few light meter apps for your phone. I have Photone, but there are a few others. If you follow their directions you should be able to at least roughly dial in enough light. Seedlings are good at 100-300PPFD, and then it goes up from there.
Herb & Suds
Well-Known Member
Nah
I would consider sticking to the light
The sun is so powerful if the plant gets used to it the lighting has a less profound effect IMO
Afghan_Landrace
Member
I am using Photone to measure PPFD, it's close to 200 at the top of the plant with these lights.
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Smokenpassout
Well-Known Member
I give them 24/7 light as soon as the sprout. Usually a single 65 watt cfl is a nice soft starter. I keep them on cfl’s until they are 5 to 6 set of leaves and move them under the blurple leds.
Horselover fat
Well-Known Member
I wish someone did a study using the same dli for 18/6, 20/4 and 24/0 veg. I suspect there wouldn't be much difference.
For seedlings I just use led bulbs. Or a led bulb and a cfl like in this photo to up the temp in my cabinet a little (led is like 3w and the cfl 11w). I moved them under the big lights very soon after this photo, because they didn't fit under the small lights anymore.
For seedlings I just use led bulbs. Or a led bulb and a cfl like in this photo to up the temp in my cabinet a little (led is like 3w and the cfl 11w). I moved them under the big lights very soon after this photo, because they didn't fit under the small lights anymore.
coreywebster
Well-Known Member
I suspect with the dli been equal 20/4 would beat the other options.
Star Dog
Well-Known Member
If i understand dli that would mean more light for 18 hrs and less light for 24hrs to = roughly the same?
That being the case I'd expect the 24 hrs with less light to do better, but idk it would be interesting to see a dli test.
Just a thought based on logic and part fact... Leafs with 24hrs are actively making starches absorbing Co2 etc 24hrs, plants with a dark period don't absorb Co2 and don't make starches but they consume starch that can't be replaced until the light comes on and photosynthesis gets going again... So all being equal might not be equal?
You can test leafs for starch using iodine + acetone, after a dark period leafs are empty the plant needs time after the light comes on before it can replenish and supply food to the plant again.
That being the case I'd expect the 24 hrs with less light to do better, but idk it would be interesting to see a dli test.
Just a thought based on logic and part fact... Leafs with 24hrs are actively making starches absorbing Co2 etc 24hrs, plants with a dark period don't absorb Co2 and don't make starches but they consume starch that can't be replaced until the light comes on and photosynthesis gets going again... So all being equal might not be equal?
You can test leafs for starch using iodine + acetone, after a dark period leafs are empty the plant needs time after the light comes on before it can replenish and supply food to the plant again.
