Learn how to grow lettuce from seed, improve germination rates, extend your growing season, and choose the right lettuce varieties for you.
How to Grow Lettuce From Seed
When lettuce is mentioned, many people think of the standard iceberg lettuce found in supermarkets and restaurant salads. But that is changing quickly with the growth in popularity of different types of lettuces, mainly due to the flavors and colors that they offer. When you grow lettuce from seed at home, you can choose from the full spectrum of seed that’s available.
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At farmers markets, health food co-ops, and organic food stores, a big variety of lettuce types have cropped up. Their colors range from deep red to mottled green to almost white. And their flavors vary from noticeably sweet to tangy to slightly bitter.
(Interesting side note: Iceberg lettuce, originally bred as a hybrid, is now offered in open-pollinated varieties and has been around long enough to be considered by some as an “heirloom”!)
Eating With the Seasons
We have come to expect lettuce year-round. We’ve been educated by the supermarkets about what our vegetables should look like, what they should taste like, and when they should be available. And for most of them, we expect them to be available all year.
Many people are surprised to learn that lettuce is a cool-season crop. It will bolt, or go to seed, readily during late spring and early summer months.
Infographic: “Save Our Seeds”
Where I live, it is best to plant lettuce early in the spring and then again in late summer or early fall when the temperatures start to cool off.
Better Lettuce-Seed Germination
Lettuce seeds won’t sprout when soil temperatures are above 80°F. But they will start to germinate as low as 40°F, making them ideal for early- and late-season planting.
When temperatures are too high, a plant hormone is produced that stops the germination process. This is called thermo-inhibition.
This trait is a carryover from wild lettuce that originated in the Mediterranean Middle East, where summers are hot with little moisture. If the lettuce seeds were to sprout under these conditions, they would soon die out and the species would go extinct.
Choose Heat-Resistant Lettuce
Thanks to traditional plant breeding, several varieties of lettuce have been selected for heat-tolerant characteristics. And some of these are open-pollinated, meaning you can save the seeds from year to year.
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Some examples are Saint Anne’s Slow Bolting, Summertime, Black Seeded Simpson, and Jericho. Just because these are heat-tolerant doesn’t mean they will grow through the summer, though. It only means that they won’t bolt or turn bitter quite as quickly.
Grow Lettuce From Seed: Tips and Tricks
Thanks to ongoing research on lettuce traits, there are some techniques home gardeners can use to extend the sprouting season for lettuce seeds into the warmer months.
The optimum soil temperature for most lettuce seeds is 68°F, with some varieties sprouting in the 40–75°F range. The temperature of the soil must be taken—not just the air temperature, which can be several degrees different.
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Imbibing or soaking the seeds in cool water for 16–24 hours in a well-lit area before planting will increase the germination percentages greatly.
Red light has been found to be the best color for encouraging germination, but if you don’t have access to a non-heating red light, sunlight or full-spectrum light is almost as good.
In warm conditions, soaking the seeds in the dark can actually decrease their germination rates. And soaking for less than 16 hours has little to no positive effect on germination rates.
Extending the Lettuce Season
Successful methods of extending the season for lettuce in the garden include laying a thick mulch of straw or wood chips on the ground at least 1-1/2 to 2 inches deep. This insulates the soil from becoming too hot and helps to preserve moisture in the soil.
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Lightly shading the lettuce plants can provide enough of a temperature drop to keep them from bolting, sometimes buying you 3–5 weeks. Shade can come from a shade cloth or a row cover on a low tunnel, or by companion-planting tall, wide-leafed plants such as some types of pumpkin.
The traditional rule of thumb of “plant early and plant often” can be adjusted for lettuce as “plant late and plant often.” When temperatures start to drop, be ready to start more lettuce seeds for a second harvest in the fall.
What Do You Think?
What are your favorite tricks for growing lettuce, and what are your favorite varieties? Let us know in the comments below!
This is an updated version of an article that was originally published on May 22, 2014. The author may not currently be available to respond to comments, however we encourage our Community members to chime in to share their experiences and answer questions!
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Marjory Wildcraft is the founder of The Grow Network, which is a community of people focused on modern self-sufficient living. She has been featured by National Geographic as an expert in off-grid living, she hosted the Mother Earth News Online Homesteading Summit, and she is listed in Who’s Who in America for having inspired hundreds of thousands of backyard gardens. Marjory was the focus of an article that won Reuter’s Food Sustainability Media Award, and she recently authored The Grow System: The Essential Guide to Modern Self-Sufficient Living—From Growing Food to Making Medicine.