Customers love lettuce in the summer, but lettuce itself doesn’t love the summer heat. Depending on where you live, growing summer lettuce might seem impossible. However, from Arizona to the deep southern U.S., even the toughest salad environments have growers who produce nice lettuce year-round—and so can you.
That said, it’s not as simple as just continuing to sow lettuce seed. Growing summer lettuce involves more work, and you need a few things to succeed. I’ve put together a small list of considerations to help you determine whether growing summer lettuce is indeed for you.
1. Seed Cost
When it comes to the summer heat, not just any lettuce will thrive. Some will bolt fast or refuse to grow at all. So it’s important to seek heat-tolerant varieties from your purveyors. Of course, heat-tolerant lettuces can be more expensive, too. So in order to make these crops worth your while, consider whether you can get these more expensive seeds consistently to maturity.
2. Regulating Temperature for Germination
Because lettuce seeds germinate at between 65 and 75 degrees Fahrenheit, you might not be able to seed lettuce directly into the soil. Using some soil mix and trays is essential. You also must keep those trays from going directly into the greenhouse—that soil needs to stay cool, too. I recommend a cellar or even a few hours in a cooler with ice. Anything to keep the temperature within that ideal germination range to ensure you get the most from the slightly more expensive seed.
3. Misting and Shade Cloth
I’ve had the most success growing summer lettuce here in 6b, where summer temperatures are regularly in the high 80s and 90s, with misting. Salad crops need a good misting every few hours when the sun is really hot to keep them happy, cool and growing. In the humid south where it rarely cools off, a night misting might help as well. Some growers couple that with 30 percent shade cloth to reduce the intensity of the sun. They might take the cloth off once the plant is established, or leave it on if the sun maintains its intensity. So if you believe your climate will require it, shade cloth and overhead irrigation is an important investment to consider when deciding on summer lettuce.
4. Consistent Watering
The other factor beyond misting is watering. In order to avoid overly bitter crops, water must be consistent and plentiful. If possible, the soil should never fully dry out. This can be done most efficiently with drip irrigation. Landscape fabric also helps control the moisture better, as will having soil high in organic matter.
5. Early Morning Harvests
If you can’t get to your fields at or before dawn, summer lettuce presents some challenges. I recommend cutting the lettuce long before the sun has fully come up. The lettuce should be immediately washed in cold water and chilled to retain shelf life. If you have limited cooler space or don’t have a way to cool down your wash water, then consider skipping summer lettuce. Without the ability to really get the lettuce cold, it will not hold well for your customers.
If all that sounds manageable for your farm, however, summer lettuce could be your new niche.