Herb Seedlings Toppling Over
Answered by: Conrad Richter
Question from: Sonya Monts
Posted on: April 02, 2004

I ordered about 20 different seed packets (most cullinary) from Richters at the beginning of this year. After reading the backs of the packets, I started the ones I could as directed about 2 1/2 weeks ago in peat cells placed in covered trays. I have them in a south facing window with 2 regular house lamps (not flourescent) and mist water each morning. I am concerned because the seeds sprouted, but the baby stems seem to be very long and weak. Some have even already toppled over. Any advice on what I could be doing wrong? I want to re-start some new peat cells this weekend, hopefully in time to transplant outdoors here in Western NC. Thanks for the help - I won’t give up!

Despite putting the seed trays near a window and adding the supplementary lights, the elongated stems is a sure sign that light is a problem. The seedlings are "reaching" for the light in the hopes of getting closer to the source, but they fail to get close enough and they topple over.

The type of lights is another problem. Ordinary incandescent lights put out the wrong kind of light for most herb seedlings. These lights put out more of the red end of the light spectrum and little of the blue end. Most plants are programmed to respond to red light by "reaching" as you have seen. Compounding the problem, incandescent lights also put out too much heat that can sometimes be detrimental to seedlings. Too much heat (especially when the light is weak) causes seedlings to respire more than they should, thereby exhausting whatever food that the seedlings are able to manufacture by photosynthesis.

I would suggest moving the trays to a brighter window if possible, as a first step. I would still keep the supplementary lights, but I would replace one of the bulbs with an energy-saver fluorescent type that can be screwed into the same sockets as the incandescent bulb. I would set the fluorescent light 6-8 inches above the seedlings. The other light with the incandescent bulb should be further away from the trays, perhaps 12-24 inches to minimize the heat. Although incandescent lights put out too much red and too little blue, an incandescent light combined with fluorescent lights gives a more balanced light that is closer to what plants get outdoors.

If possible add another fluorescent light because even the two lights is probably not enough light for the seedlings -- you can tell that if your seedlings continue to "reach". You won’t be able to eliminate all "reaching" but you should be able to reduce it considerably. And pay close attention to the heat output: if the arrangement of lights is pushing the temperature above 85 degrees Fahrenheit (30 degrees Celsius) then you will have to adjust the distance of the lights from the trays.

One other thing, the lights should not be on 24 hours a day: they should be set to 16-20 hours on and 4-8 hours off. And keep the lights on even during the day.


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