
This week’s post is a combination of two features. First explorations of a myth about lettuce seeds needing light to germinate, and how to germinate lettuce when it’s hot. Second a social platform just for farmers, homesteaders, and agriculture professionals, without paid advertising.
Do Lettuce Seeds Really Need Light to Germinate?
Robert Pavlis runs a website devoted to exploring and, when needed, exploding Garden Myths. One such legend is that lettuce seeds need light to germinate. I always cover my lettuce seeds with soil, trying not to sow too deeply. They grow.
Robert Pavlis read the research
He conducted his own experiments.
Here are results of his tests of lettuce germination
- The seeds he tested germinated in the dark, but light increased the rate of germination. So, lettuce seeds can germinate in the dark.
- Even small amounts of light do improve germination.
- Covering seeds with a thick layer of soil either prevents germination or stops the growth of the newly germinated seed.
- Pavlis recommends: Too much soil over small seeds is never a good idea.

Dr. Deno’s Seed Starting Books
from 1993, in the USDA National Agricultural Library, have a lot of valuable information on starting seeds. You can read them on the Garden Myths site.
2022 Italian Study
In 2022, the Italian Journal of Agronomy published an article, Indoor germination and seedling growth of green and red lettuce under LED-light spectrum and subsequent effect on baby leaf lettuce, by Cristian Hernández-Adasme, Herman Silva and Victor Escalana.
The light requirement for germination depends on the spectrum and intensity of the light.
Low light intensity can reduce photosynthesis, and an inadequate light spectrum can slow plant growth and reduce crop quality. The study investigated the effect of various light wavelength spectra at low intensity on the germination and growth of red (Carmoli) and green (Levistro) lettuce seedlings, using a temperature-controlled space, and LED lights for 12 hours or darkness.
The second trial (using the same light conditions) compared yield, quality, leaf color and stress-resistance to lettuce seedlings grown under the same experimental conditions and under natural light.
In the third trial the LED-grown seedlings were transplanted into a hydroponic greenhouse under natural light, to assess the impact on mature baby lettuce plants.
The study showed:
- Green lettuce seedlings had higher weight than the red seedlings.
- Red light reduced the percentage germination.
- Blue light reduced germination time and increased the number of germinated seeds compared to darkness.
- Fresh weight was higher under red light and the BGR2 spectrum mix (29% blue, 53% green 17% red and 1% far red).
- Blue and full-spectrum lights applied to lettuce seedlings increase the fresh weight after transplanting.
- High-blue component lights increased the dry matter percentage, and chlorophyll content of lettuce seedlings, but the difference did not hold up after transplanting.
- The anthocyanin content of Carmoli seedlings was stimulated by blue light, but even more so by natural light.
- Varying the spectrum at low intensity can positively modify the growth and biochemical characteristics of lettuce seedlings, although the effect depends on the cultivar, in particular perhaps the lettuce color.

Photo Twin Oaks Community
Conclusions
Spectrum modification at low intensity significantly impacts the different growth stages of lettuce, although the differences depend on the cultivar. High blue component lights positively affect the germination process by accelerating it and increasing germinated seeds per day. Also, high blue component lights improved the DMP, CHL a/b ratio, and ANT concentration in lettuce seedlings. In addition, broad-spectrum light such as BGR2 positively affects the FW of the seedlings and, together with blue light, increases FW by about 18% in the mature lettuce grown under natural light conditions. On the other hand, LED technology would be feasible to use in vertical farms for seedling production because of its advantages of long service life and low power consumption. In addition, the yield per unit area in controlled growth systems can be up to twice as high as in traditional agriculture.
This information is modified (the Conclusions are copied verbatim) from the website linked above, under a Creative Commons Attribution-NonCommercial 4.0 International Deed.

Sustainable Market Farming, 2nd Edition
Research has shown that lettuce has better emergence in hot weather if sown between 2–4 pm, because the temperature-sensitive phase of germination will then occur at night when soil temperatures are cooler. Regardless of this research, I sow it in the evening! (I just find it hard to believe lettuce germinates best sown at the hottest time of day.)
Last week, faced with temperatures of 95F (35C) and 100 F (38C), I decided to try a morning sowing. I used my usual summer method: sowing outdoors in a nursery seedbed, covering lightly with soil, watering with freshly-drawn cold water, covering the rows with ice cubes, and then shadecloth. Nothing came up. I realize this is no way to conduct an experiment! But I’ve gone back to evening sowing!
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Summer Lettuce Lessons from Southern Growers
Growing for Market magazine has a good article by Jesse Frost on growing summer lettuce in the South
A method from Au Naturel Farm in Kentucky is to set seeded trays in the walk-in-cooler for 48 hours. Pull the tray out in the afternoon and “usually by the morning time those seeds have already popped up. Using that technique we were able to get almost perfect germination every single week.”

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Ag Solidarity Network
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The November/December issue of 



The May issue of Growing for Market is out. The cover article is about wholesaling, by Jed Beach. His purpose is to encourage growers who are dissatisfied with the stiff competition in retail, to look carefully at comparative costs of selling wholesale. Receiving a lower price (wholesale) will not lead to lower income if you costs are considerably lower.
Ellen has written an upcoming book, with Forrest Pritchard, called 








Lastly, the campaign 














The September 












