Light bulbs best for seedling growing?

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Discussion Overview

The discussion centers on the effectiveness of different types of light bulbs, specifically LED, incandescent, and fluorescent, for growing seedlings, particularly tomato plants. Participants explore the impact of light color, intensity, and bulb type on plant growth and development, including issues like etiolation and spindly growth.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants suggest that LED lights may not be as effective as incandescent or fluorescent lights for plant growth, questioning the best color or wavelength for preventing seedlings from becoming tall and falling over.
  • Others argue that the effectiveness of light depends on the type of plant being grown and inquire about the specific plants in question.
  • One participant notes that incandescent bulbs have a broad spectrum emission, which may benefit plant growth, while some fluorescent and LED lights may emit only at certain wavelengths, potentially limiting growth.
  • There is a mention of specific fluorescent lamps that have been effective for plants, and a similar trend is noted for LEDs.
  • Concerns are raised about etiolation, where seedlings become spindly due to lack of light, and other issues like damping off and cutworms affecting seedlings.
  • One participant shares personal experience with tomato plants, noting that they become spindly when grown under fluorescent lights and questions whether T5 bulbs would improve this situation.
  • It is suggested that blue light may encourage leaf growth while red light may promote vertical growth, with a note that LEDs can be produced in various colors.
  • Another participant emphasizes that the color perceived by humans may differ from what plants require, indicating that proper wavelengths are essential for plant health.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of various light types and colors for plant growth, with no consensus reached on which is definitively best for seedlings. The discussion remains unresolved regarding the optimal lighting solution for specific plant types.

Contextual Notes

Participants mention various factors influencing plant growth, including light intensity and distribution, but do not reach a consensus on the best practices or solutions. There are also references to specific issues like etiolation and damping off, which may complicate the discussion.

Questor2
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I have heard that LED light is not as good for growing plants as incandescent or fluorescent, can someone explain this? And what is the best color or wavelength to keep seedlings from getting all tall and falling over...? or is it the intensity?
 
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Probably depends on the type of plant. Which plants are you working with? (some plants have been legalized lately) Can you post links to the reading that you have been doing that is confusing to you?
 
Incandescent bulbs have broad spectrum emission, so all the wavelengths plants use are present.
Some fluorescent and LED lights emit only at certain wavelengths. This can be limiting for plant growth.
Other fluorescent and LED lights use mixes of phosphors that broaden the wavelengths they give off.

For years there have been specific fluorescent lamps that work well with plants. Recently, the same is true for LEDs.
Plants growing supply stores will have these.

The intensity of the light (rather than the wavelengths) may have to do with the stringiness of the plants.
 
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There are "kinds" of falling over:
spindly yellow seedlings from lack of light - etiolation. https://en.wikipedia.org/wiki/Etiolation
-- suggestions for bulbs - note that LED's are okay, not the very best best but save money: https://www.todayshomeowner.com/how-to-grow-houseplants-in-artificial-light/
Damping off - fungus disease - from soil with the disease spores present.
https://en.wikipedia.org/wiki/Damping_off - sterilize the soil in an oven at 275 °F for an hour, and clean the pots/trays with bleach, do not overwater.
Cutworms - bugs that level seedlings.
https://en.wikipedia.org/wiki/Cutworm - control with insecticides.

Since we cannot tell exactly what happened, I gave it the shotgun approach. People often think that light is the problem with spindly seedlings or ones that seem to fall over for no reason. You get to work out which problem you actually have.
 
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Moved to Biology.
 
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Well mostly needing the info for tomato plants that I grow every year with Growlux flourescents and every year they start out nice and then grow a few inches till they hit the light bulb which I keep moving upwards, but after they get about 4" high they get spindly in the stems, while the ones I see in a greenhouse with natural light have nice thick stems... and I am using a similar starting mix. With just natural light from a window they grow much weaker and tall and thin. So would the new T5 bulbs prevent this? I see some of the systems cost like $250, for which I could buy all my tomato plants for years and years, so need something less costly!
 
Bluer light tends to encourage more leaf growth, redder light encourages vertical growth.
LEDs can be in any colour you like, which is not the case with other light systems.
They don't as makers claim last 10x longer though, maybe 2 or or 3,
 
Questor2 said:
Well mostly needing the info for tomato plants that I grow every year with Growlux flourescents and every year they start out nice and then grow a few inches till they hit the light bulb which I keep moving upwards, but after they get about 4" high they get spindly in the stems, while the ones I see in a greenhouse with natural light have nice thick stems... and I am using a similar starting mix.
Low power systems tends to be inadequate when the green is a bit further away from the source. They are OK for lettuce, but with tomato only the top of the plant has enough light, the lower parts are still in the dark.
So it sounds like you need more distributed light, not only from top. Might want to try to 'save' the escaping light with some tin foil around the box?

rootone said:
LEDs can be in any colour you like
The color you see and the color the plant 'sees' might be entirely different... Even if the classic RGB LEDs can give light which you will see similar to a set of growth LEDs, the plants below will just 'starve'. They need the proper wavelength, not the (visible for human eye) color.
 
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