winter lettuce production
“Whether growing for home use or for commercial
production, a wide variety of lettuces and leafy vegetables
can be successfully grown in hydroponic systems.”
Germinating
No bottom heat is required to germinate lettuce seeds.
Lettuces are cool weather crops, so excessive heat can actually
delay or prevent germination. Simply cover a tray of starter
cubes with a plastic sheet or humidity dome, place under cool
fluorescent lights and wait a few days for germination. Once
the roots begin to poke out through the bottom of the cubes,
they are ready for transplanting into the NFT system.
Lighting
In northern climates, prolonged periods of short, overcast
days can dramatically slow down growth rates of lettuce.
Therefore, the judicious use of horticultural grow lights is
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often recommended. Plants need full-spectrum light, with
both the blue and red ends of the spectrum for vigorous
growth. During the vegetative growth stage, plants prefer the
blue end of the spectrum. Blue light at the 460-nm wavelength greatly influences phototropism—the tendency of
plants to lean toward the light. If plants receive enough blue
light in the 460-nm range, they tend to have a more compact growth habit. Also, blue is responsible for chlorophyll
production more than other wavelengths. Metal halide grow
lights are full-spectrum lamps, rich in the blue end of the
spectrum, and they are well-suited for lettuce production.
Advances in LED technology are also proving beneficial for
indoor lettuce production.