Romaine LettuceRomaine lettuce, also known as Cos lettuce, has long, broad, upright leaves that hold themselves bunched together as they mature. Although romaine varieties are well known for the hearts at the center of the heads, the outer leaves can also be used in salads, as a tortilla substitute for wraps, and are delicious grilled. Romaine lettuce is crisp and juicy, with a sweetness unmatched by other lettuce types. (1)

This nutrient-rich vegetable is an excellent source of minerals and antioxidants and has about 8 calories and 1 to 2 grams of carbohydrates per cup of lettuce. Romaine is low in fiber, but high in minerals, such as calcium, phosphorous, magnesium, and potassium. It’s naturally low in sodium. Plus, romaine lettuce is packed with vitamin C, vitamin K, and folate, and a good source of beta carotene, which converts into vitamin A in the body.

The nutrients in romaine lettuce provide multiple health benefits:

Vitamin C helps support the immune system, is high in antioxidants, and helps keep bones and teeth strong.
Calcium is necessary for the building and maintenance of bones, muscle function, nerve function, and blood clotting.
Vitamin K is also necessary for blood clotting. It works together with calcium to prevent bone mineral loss and fractures due to osteoporosis.
Vitamin A (from beta carotene) is a vital nutrient, necessary for health. An antioxidant, vitamin A supports cell growth and reproductive health. It also helps to maintain the heart, kidneys, and lungs. Vitamin A also supports the eyes.
Folate is a B vitamin, which supports cell division, the production of DNA, and genetic material. Folate deficiency in pregnant women can lead to complications with pregnancy, including premature birth, low birth weight, or the birth defect spina bifida.
Phosphorus works with calcium to build strong bones and teeth.
Magnesium helps enzymes function and relaxes the muscles in your body. It works with calcium to build tissue.
Potassium is an electrolyte that helps your heartbeat regularly. It supports nerve function and helps your muscles contract normally. Potassium also helps your cells to move, and utilize, nutrients efficiently. It minimizes the negative impact of sodium (salt) on the body (2)
Due to high demand, commercial growers have dedicated thousands of acres each year to growing romaine lettuce. It’s estimated that green leafy vegetables account for 20% of food-borne illnesses. This has resulted in numerous recalls of romaine lettuce in the past decade. For this reason, many consumers prefer to buy their lettuce from local farms or grow their romaine at home for a safer alternative.

How to grow:
Of the many varieties of leaf and head lettuce, most prefer full sun and temperatures between 45–80˚, making lettuce a good cool-season crop. Lettuce can withstand light frosts. But in hot weather, it will easily bolt (i.e., quickly grow vertically, flower and produce seeds)—and this process typically makes lettuce bitter. So if you grow lettuce in warmer conditions, plant it in partial shade or grow heat-tolerant varieties, like these Cherokee, Black-Seeded Simpson, Mascara, and ButterCrunch.

https://www.towergarden.com/blog.read.html/en/2015/4/_lettuce_get_growin.html

https://www.johnnyseeds.com/vegetables/lettuce/romainee-lettuce-cos/

https://www.healthline.com/health/food-nutrition/romainee-lettuce