Light bulbs best for seedling growing?

[Questor2]

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?

 

[berkeman]

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?

 

[Greg Bernhardt]

Start here
https://www.planetnatural.com/plant-light/

 

[BillTre]

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.

 

[jim mcnamara]

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.

 

[jim mcnamara]

Moved to Biology.

 

[Questor2]

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!

 

[rootone]

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,

 

[Rive]

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?

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.