• Do you need help identifying a 🌶?
    Is your plant suffering from an unknown issue? 🤧
    Then ask in Identification and Diagnosis.

health Why are my seedlings falling over?

Hi folks, wondering if someone might have an idea why a load of my seedlings seem to not be able to hold their heads up?
For info, all planted on January 31st, sprouted between February 4th and 8th (pretty quick, I reckon), humidity dome removed on 11th, and since then they have had a light about two inches above them for 12 hours daily, and a weak breeze from a fan for about 2 - 3 hours daily. Still sitting on the heating mat, so soil is at 28°C.
All looked fine until a couple of days ago, when they started dropping 🤔😬.
 

Attachments

  • IMG_20240217_134127_568.jpg
    IMG_20240217_134127_568.jpg
    171.6 KB · Views: 241
I think the high temperature is only required to germinate the seeds. Once the seedlings are up it may be better to lower the temperature. I germinate the seeds at 28 degrees also in the propagator but once the seedlings are up, I take them out and keep them at room temperature. This lowers the grow rate...
 
I moved from fluorescents to these. https://www.amazon.de/-/en/VIPARSPE...bles/dp/B0BNVFMJ5J?ref_=ast_sto_dp&th=1&psc=1

This is the type of spindly growth I got with the fluorescents. Low light is the problem & no fan will fix it.

What power do you have it on? I've seen these lights grow houseplants, so they must have some power.
I have my lights set at 40% power & fourteen inches above the seedlings.

I have never had plants that grew so strong as under these LED grow lights before.

1708177552309.png
 
I think the high temperature is only required to germinate the seeds. Once the seedlings are up it may be better to lower the temperature. I germinate the seeds at 28 degrees also in the propagator but once the seedlings are up, I take them out and keep them at room temperature. This lowers the grow rate...
Thanks Marc. I reckon that's probably the main culprit, and then too little light is probably just exacerbating the problem. Time to get them off the mat and under more light then 🙂. You guys are awesome:dance:.
 
I think the high temperature is only required to germinate the seeds. Once the seedlings are up it may be better to lower the temperature. I germinate the seeds at 28 degrees also in the propagator but once the seedlings are up, I take them out and keep them at room temperature. This lowers the grow rate...
Thanks Marc. I reckon that's probably the main culprit, and then too little light is probably just exacerbating the problem. Time to get them off the mat and under more light then 🙂. You guys are awesome:dance:.
 
Took the mats out from under them and loaded the airspace above them with all the LEDs I have. If I support the fallen with toothpicks, do you think they can still be rescued or would I be wasting my time and effort?
 

Attachments

  • IMG_20240217_144650_710.jpg
    IMG_20240217_144650_710.jpg
    147.9 KB · Views: 68
Last edited:
What power do you have it on? I've seen these lights grow houseplants, so they must have some power.
I have my lights set at 40% power & fourteen inches above the seedlings.
They are full spectrum lamps with 10W (40W equivalent) output, and at the moment I have the blue lamps running on full power about 2 inches above the seedlings. The reason I have them so low is that I reckoned they have nowhere near the power of a "proper" grow lamp, and I had read that having the light too high up often results in leggy seedlings, since they try and stretch towards the light. What I obviously hadn't anticipated was the seedlings growing far faster than they should due to the high soil temperature 😳.
I am now thinking that the lights may be too low after all, but I'm not sure whether I should already raise them, or wait and see whether a combination of lower soil temperature and close light might help some of the "skinny giants" to recover first 🤨.
The good thing is that, after losing a lot of germinated seedlings last year - no doubt due to the same mistake - I planted loads of each type, so I should still have enough viable ones to give me a couple of plants of each type, even if these ones don't recover. All part of the learning process , but it's great to know that you folks are around to share your experience🤗.
 
They are full spectrum lamps with 10W (40W equivalent) output, and at the moment I have the blue lamps running on full power about 2 inches above the seedlings. The reason I have them so low is that I reckoned they have nowhere near the power of a "proper" grow lamp, and I had read that having the light too high up often results in leggy seedlings, since they try and stretch towards the light. What I obviously hadn't anticipated was the seedlings growing far faster than they should due to the high soil temperature 😳.
I am now thinking that the lights may be too low after all, but I'm not sure whether I should already raise them, or wait and see whether a combination of lower soil temperature and close light might help some of the "skinny giants" to recover first 🤨.
The good thing is that, after losing a lot of germinated seedlings last year - no doubt due to the same mistake - I planted loads of each type, so I should still have enough viable ones to give me a couple of plants of each type, even if these ones don't recover. All part of the learning process , but it's great to know that you folks are around to share your experience🤗.
Not sure about the temperature being a major contributing factor, not saying it is not, just never experienced that myself.

Anyway, I believe insufficient light is absolutely the problem. When you say they are 10W that means they are using 10W of power from the outlet. Looking at the linked page on Amazon, I see the following: Untitled.png

This illustrates the spectrum and PPFD of these lights. It appears they have quite a bit of orange/red output, and not much blue. "Full spectrum" is great for mature plants, but new seedlings need a lot more blue. Also, peppers have a Daily Light Integral (DLI) of about 30. New seedlings may only require a DLI of 20.

To achieve a DLI of 20 with a 16 hour a day photoperiod, you would need a PPFD of ~347.

There’s a law of physics called the Inverse Square Law. This law says if you know the intensity of your grow light at one height, for example 1000 micromoles at 18 inches, then every time that height is doubled, the light intensity is reduced by 75%.
 
I agree with the others about the lights being the problem, but you may also consider using a small fan on the seedlings. Not hurricane force winds, but a very gentle breeze can help stimulate the plant to strengthen the stems.
 
Last edited:
Not sure about the temperature being a major contributing factor, not saying it is not, just never experienced that myself.

Anyway, I believe insufficient light is absolutely the problem. When you say they are 10W that means they are using 10W of power from the outlet. Looking at the linked page on Amazon, I see the following: Untitled.png

This illustrates the spectrum and PPFD of these lights. It appears they have quite a bit of orange/red output, and not much blue. "Full spectrum" is great for mature plants, but new seedlings need a lot more blue. Also, peppers have a Daily Light Integral (DLI) of about 30. New seedlings may only require a DLI of 20.

To achieve a DLI of 20 with a 16 hour a day photoperiod, you would need a PPFD of ~347.

There’s a law of physics called the Inverse Square Law. This law says if you know the intensity of your grow light at one height, for example 1000 micromoles at 18 inches, then every time that height is doubled, the light intensity is reduced by 75%.
Thanks for taking the time to explain in detail. TBH I had had a look at the graphs, but without the necessary background knowledge of how to interpret them or explanations of what the numbers on the colourful one are supposed to represent, they might as well have been a Rohrschach test for acid heads :think:.
I don't suppose you have a link to an idiot proof explanation for beginners of the information and terminology for lighting requirements, do you? I reckon something like that would help me get my aging brain up to speed.
 
Thanks for taking the time to explain in detail. TBH I had had a look at the graphs, but without the necessary background knowledge of how to interpret them or explanations of what the numbers on the colourful one are supposed to represent, they might as well have been a Rohrschach test for acid heads :think:.
I don't suppose you have a link to an idiot proof explanation for beginners of the information and terminology for lighting requirements, do you? I reckon something like that would help me get my aging brain up to speed.
Finn,

There are several webpages, and even some videos, that explain horticultural lighting; Photo-synthetically Photon Flux Density (PPFD), Photo-synthetically Active Radiation (PAR), Correlated Color Temperature (CCT), etc., and how they affect plant growth. I really cannot recommend one over another. If you search using the above terms, I am sure you will encounter more information than you need.
 
test for acid heads :think:.
I don't suppose you have a link to an idiot proof explanation for beginners of the information and terminology for lighting requirements, do you? I reckon something like that would help me get my aging brain up to speed.

I went from Floursents to LED grow lights. Looked everywhere for how to use this new light source that could burn my seedlings up.
Going from Youtube video to another I saw growers using all types of costly light meters measuring light intensity of different lights.

I got lucky & found a video on how far & how much power to use for my seedlings. Fourteen inches above & power set to 40%.
As for all the: https://www.ledsupply.com/blog/breaking-down-the-important-led-grow-light-metrics/

Check this this video out on fixing leggy seedlings he has some good points.

 
Last edited:
Back
Top