Let Us Eat Lettuce

By Glenn I. Teves, UH College of Tropical Agriculture and Human Resources

Many New Year’s resolutions will be related to modifying our diets, losing weight and adopting healthy lifestyles. Increasing the consumption of greens is a great start to improved health. Once a lowly, prickly weed, today’s lettuce is King of the Greens, and closely related to many weeds including dandelion, milkweed, floras paintbrush, and Spanish needles.

Native to the Mediterranean basin from the Ethiopian highlands to Iran, lettuce was cultivated before 4500 BC as evidenced by paintings in Egyptian tombs. The Greeks considered it an appetite enhancer, consuming it before the main dish, while the Romans considered lettuce a narcotic similar to opium and usually ate it at the end of a meal.  Both its common and Latin names originate from its ability to produce milky sap, and it’s this sap that’s believed to be sleep-inducing. Modern research has confirmed that lettuce concentrates and absorbs lithium, a mood-stabilizing chemical.

Many types of lettuce were developed, including cos or romaine, looseleaf, butterheads, and crispheads, and intermediates between these groups. Called Cos by the Greeks and Romaine by the Romans, this upright leaf lettuce was a mutual favorite. Columbus is credited with introducing lettuce to the new world. More recently, lettuce varieties developed by the French including Batavian or summer crisp, a heat-tolerant type intermediate between crisphead and looseleaf types.

 Tossed salad once meant head lettuce, cucumbers, and tomato. In the 80s, a salad rebirth occurred in California fueled by European salad styles, and refined by upscale restaurants, creating a whole new salad eating experience. Today, lettuce can be found in all shapes, sizes, and mixtures, and include whole heads, hearts, cut salad mix, baby lettuce, and also microgreens, a gourmet confetti made from a variety of crops and harvested at the seedling stage. Mesclun is a mix of lettuces and greens from east and west that add color, texture, and depth to salads.Lettuce is a good source of vitamin C, beta-carotene, iron, calcium, folate, and dietary fiber. Romaine and leafy lettuces have six times the vitamin C and five times the vitamin A of crisphead types. Usually the rule of thumb is the darker the greens, the more nutritious the leaf. Crisphead lettuce is less bitter than other types, but also less nutritious due to the high water content. California is considered the ‘salad bowl’ of the nation, but doesn’t come close to China, who produces over 50 percent of the world’s production, and where lettuce leaves and stems are commonly cooked.

To grow, lettuce should be kept constantly moist to prevent build-up of milky sap, creating a bitter taste. Lettuce is a cool season vegetable, favoring temperatures of 75 degrees F or less. An easy way to have an ample supply of young lettuce is to sow seeds in a deep tray with potting mix, either by broadcasting or seeding in rows. After three to four weeks of initial growth, lettuce can be harvested once or twice a month for two to three months depending on the weather. Use a scissors to cut leaves about three-quarters of an inch or more above the surface. Mist plants to keep them cool during the heat of the day. Sprinkle with one teaspoon per gallon fertilizer, such as fish emulsion or ones with slightly higher nitrogen content, every seven to 10 days and after each cutting, and cut until the lettuce becomes bitter. You can also purchase lettuces mixes instead of individual varieties. Heat-tolerant lettuce varieties grow well in the spring into the summer, and include Manoa, Buttercrunch, Summer Bibb, Summertime, Concept, Sierra, Jericho, and many oak leaf types. Another way to extend your lettuce season is through the use of shade cloth or screen over the plants.