For the home gardener Lettuce (Lactuca sativa) is another one of those harbingers of spring. It is as a leaf vegetable belonging to the Asteraceae (or Compositae) family, which is known as the aster, daisy, or sunflower family. The name of the genus is derived from lac, the Latin word for “milk”which refers to the plant’s milky juice.
Lettuce originated in the Mediterranean basin and has been served in dishes for more than 4500 years. The earliest depiction of lettuce is in the carvings at the temple of Senusret I (1926 BC) at Karnak in Egypt being served to the God Min, who considered it sacred. It also appears in writings such as The Contendings of Horus and Set.
Lactucarium is a mild sedative like substance that is contained in all types of lettuce. Both the Romans and Egyptians took advantage of this property eating lettuce at the end of a meal to induce sleep. However, the dictatorial Emperor Domitian (81-96 AD) was known for serving it at the beginning of his feasts, so he could torture his guests by forcing them to stay awake in the presence of the Emperor.
The Romans cultivated lettuce extensively and eventually introduced it to Europe. Lettuce was brought to the Western Hemisphere shortly after its “discovery” by Columbus though it is unclear whether he was actually responsible for its introduction. Thomas Jefferson had 19 varieties of lettuce growing in his garden at Monticello.
There are hundreds of cultivars of lettuce organized for leaf shape and color, field and shelf life. Lettuce also varies widely in taste and texture. Some lettuces are mild and tender while others are crunchy or bitter. While accumulating a worldwide gene pool of lettuces, the USDA found red, yellow varieties, and blue-green varieties of lettuce.
Lettuce (of all types) is the second most popular fresh vegetable in the United States behind #1 potatoes. The average American eats approximately 30 pounds of lettuce each year.
Butterhead forms loose heads. Its leaves have a tender and buttery texture and mild taste. Popular varieties include Boston, Bibb, Buttercrunch, and Tom Thumb.
Crisphead forms tight, dense heads that resemble cabbage. The bitterness has been bred out of the strain and they are generally the mildest of the lettuces. They are highly valued more for their crunchy texture rather than flavor. Crisphead is also known as Iceberg lettuce. The name Iceberg comes from the way the lettuce was transported in the United States, starting in the 1920s on train-wagons covered in crushed ice, making them look like icebergs.
Looseleaf doesn’t grow to form lettuce heads, but is instead the leaves are joined at the stem. They generally have tender, delicate, and mildly flavored leaves in colors ranging from light green to red or purple. Looseleaf varieties include: Black Seeded Simpson, Lolla Rossa, Green Ice, Buttercrunch and Mighty Red Oak.
Summer Crisp, also called Batavian, forms moderately dense heads with a crunchy texture. This type is intermediate between iceberg and looseleaf types.
Romaine, also called Cos, grows in a long head of sturdy dark green leaves with a firm rib down the center. This lettuce has gained tremendous popularity in the past decade as the key ingredient in Caesar salads. Unlike most lettuces, it is tolerant of heat.
Chinese lettuce types generally have long, sword-shaped leaves that don’t form heads. They are characterized by a bitter and robust flavor. Chinese lettuce cultivars are divided into “stem-use” types and “leaf-use” types and are used in stir-fried dishes and stews.
In many countries, lettuce is eaten cold and raw, in salads and on sandwiches, hamburgers, tacos, and in many other dishes. In some places, including China, lettuce is typically eaten cooked and the stem is as important as use of the leaf.
Lettuce is a low calorie food and is a source of vitamin A and folic acid. The deeper the color lettuce leaves the higher the level of nutrients.
Selection and Storage
Lettuce is a very delicate vegetable and great care should be taken when selecting and storing. In fact, lettuce is a vegetable that is “immune” to preservation. You can’t freeze it, can it, dry it, or pickle it.
Be sure the leaves show no signs of wilting, slim, or dark spots or edges. Remember when selecting your lettuce that the darker outer leaves are the most nutritious.
Lettuce tends to keep well in plastic bags in the crisper section of the refrigerator. Iceberg lettuce has the longest storage life, lasting around two weeks. Romaine lasts for about ten days, and butter head and loose leaf types last approximately four days. The very delicate baby lettuce or micro-greens don’t last very long, so it’s best to buy only as much as you need at one time and use immediately.
Salad greens should not be stored near fruits that produce ethylene gases (like apples) as this will increase brown spots on the lettuce leaves and increase spoilage. Greens that are bought in bunches should be checked for insects. Those leaves that have roots should be placed in a glass of water with a bag over the leaves and then placed in the refrigerator.
Generally lettuce is eaten raw, so remove any browned, slimy, or wilted leaves. For all lettuce types, you should thoroughly wash and dry the leaves to remove any dirt or lingering insects. If you eat lettuce often, a salad spinner is a time saving investment. Simply rinse the leaves and place in the spinner to remove the excess water.
In addition to their most common use in salads, you can also braise, steam, sautè and even grill certain lettuce varieties to create a wonderful and different taste treat. Try halving a head of radicchio, romaine or endive lengthwise, and brush with extra virgin olive oil, and grill until they soften and just begin to brown.