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lighting Light distance from seedlings?

JH4FSU

JH4FSU

What is the proper light distance from seedlings? I know it matters with what type of light, but a low watt full spectrum grow tube from Walmart for example. Researching on the internet of course you can get 2 totally different answers, one I looked at said 1-3 inches, the other said 18-24 (assuming that is probably a fairly strong light) I suddenly have to go out of town for the weekend so they are fresh under the light as of this morning, they been growing in the seed trays that have little cheap full spectrum led’s in them, but now under the tube light. Here’s the
Light in question, i have some Mattapenos that popped first and are trying to get leggy before the others. Just don’t want to come home to a disaster. Thank you in advance for any help

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Great Value 2 ft Selectable Spectrum LED Grow Light, 20W, Linkable - Walmart.com

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alkhall said:
Really excellent growth. My oldest are just at four weeks.
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This is from my 23 grow.

This season. 2 weeks ago.

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alkhall said:
Yes, they do have a little way to go...

Have they stopped stretching with the new fixture?
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Most, if not all, of them do seem to have stopped getting taller. In fact their growth in many cases seems to have completely stalled, although most are finally starting to get their first set of true leaves. I just had a look back at the journal I kept last year, and the first 2 seedlings had their first true leaves at 36 days after planting, so given that I'm now on day 38 for the first of this year's crop, I'm slightly ahead of the game in comparison. Not surprising, when you consider this was my setup last year :eek:. I'm surprised anything survived at all :party:.
 

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FinInGermany said:
Most, if not all, of them do seem to have stopped getting taller. In fact their growth in many cases seems to have completely stalled, although most are finally starting to get their first set of true leaves. I just had a look back at the journal I kept last year, and the first 2 seedlings had their first true leaves at 36 days after planting, so given that I'm now on day 38 for the first of this year's crop, I'm slightly ahead of the game in comparison. Not surprising, when you consider this was my setup last year :eek:. I'm surprised anything survived at all :party:.
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They may appear to have stopped growing, but most likely are busy developing root structure.
 
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FinInGermany said:
Does this mean that there are some types of chillis which you shouldn't you shouldn't put with certain others under the same light, or are the differences in tolerance not so dramatic?
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I think all can be in the same light but others get easier rolled leaves than others. But there are many things that may make it happen. Firstly the plant gets too much light, the root revoplement is not big enough to handle the light. Secondly, if the container is not too big it gets dried too fast. Thirdly it can be over fertilized and lastly the plant is just weaker than others. But if you have some conditions and others do well and others not. Then it means it is just weaker than others. Then your only choice is to give it less light.
 
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The light on the right is a spider farm sp1000, basically the same power i think. I'm running them at about 40% which i think is just right?

ps when the seed shell gets stuck on the young sprout, is it ok to get some nail clippers and shear off the edge of the shell? many seem to be stuck..... i watched a video where a man would trim the side off the seed to help the seed crack open.
 
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FinInGermany said:
At a guess, I think your lights are probably around 6 to 8 inches above the seedlings, which seems to me a little close for LEDs. Running at 40% would of course mitigate that to an extent, so you should be OK, but better to wait for someone who really knows what they're on about to chime in 😁 .
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I put mine at 14" above after watching Youtube about starting Pot seeds that's all I could find at first.
Plants all grew fine.
 
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Same subject but a slight digression. Anybody know how reliable these light meter apps for smartphones are? Downloaded one out of curiosity, as I'm waiting for a light meter to arrive on Tuesday. No idea what the PAR values at the seedling tops are, since I can't justify the expense as a hobby grower, but the app says they are being subjected to between 13000 and 40000 LUX, depending on their position. Are these values credible? And if so, acceptable?
Most of the plants seem to be fine with this, but as can be seen from the third photo, a couple of them are clapping their leaves above their heads. Do I need to raise the light, or do you reckon these seedlings will be ok?
 

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FinInGermany said:
Same subject but a slight digression. Anybody know how reliable these light meter apps for smartphones are? Downloaded one out of curiosity, as I'm waiting for a light meter to arrive on Tuesday. No idea what the PAR values at the seedling tops are, since I can't justify the expense as a hobby grower, but the app says they are being subjected to between 13000 and 40000 LUX, depending on their position. Are these values credible? And if so, acceptable?
Most of the plants seem to be fine with this, but as can be seen from the third photo, a couple of them are clapping their leaves above their heads. Do I need to raise the light, or do you reckon these seedlings will be ok?
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Which app are you using?
 
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I am using Photone on my iPhone, which appears to be most accurate. (Thanks to @Tdub for bringing it to my attention) There is a video of it being tested against a $500+ Apogee PAR meter, but I do not have the link.

It can display PPFD, DLI, Luminance (Lux), and CCT.

The basic free version is somewhat limited, and I do not believe it has the option for LED lights enabled.

I coughed up $80 for the lifetime Pro version. Also, it requires a diffuser, which I purchased for another $25.

However, I have noticed that the CCT (Correlated Color Temperature, e.g. 6500K) is a bit wonky.

I have a thread where I have compared several different lamps/combinations of lamps, mostly fluorescent.

Anyway, to try to answer your question; I also saw videos that claim to provide calculations whereby one may determine PPFD (which is the critical factor) from LUX readings obtained with a regular light meter.
 
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