If you think of salad you probably think of lettuce. Maybe crunchy iceberg or crisp romaine in a caesar salad. These two cultivars might be the most common in the US, but they aren’t the only kind of lettuce out there. There are plenty more – colorful leaf lettuces, lettuce grown for it’s oily seeds or thick stalks.
The scientific name for lettuce is Lactuca sativa. Sativa is a common name for crop species since it means ‘cultivated.’ Think Eruca sativa (arugula), or Cannabis sativa (marijuana and hemp). Lactuca is from the Latin word for milk – lac – and is a reference to the milky substance that oozes out of freshly cut lettuce leaves. If you’re thinking ‘huh, don’t cut dandelion’s ooze a milky substance too?’ you’re right! Both lettuce and dandelions are in the same subfamily of the Aster family. Besides the bitter, milky juicy they have another common trait – flower shape. Think of a dandelion flower – lettuce flowers look just the same, except smaller and there are more flowers on each stem.
Cultivated lettuce developed a long time ago in the Fertile Crescent. This region stretches from the Nile river over to the Persian Gulf. It has moist and fertile land (in comparison to the surrounding arid land) and is where many early civilizations developed. Early crop domestication and irrigation in this region was a major step in the developing of these early civilizations.
Some sources say Egypt was the region of lettuce origin because a bed of lettuce is one of the symbols of Min, the god of fertility. According to Wikipedia “Egyptians believed [lettuce] to be an aphrodisiac, as Egyptian lettuce was tall, straight, and released a milk-like substance when rubbed, characteristics superficially similar to the penis.” Alternatively lettuce may have developed in the area between the Tigris and Euphrates rivers because more wild relatives found here.
Regardless of the location of lettuce origin the species has been bred for centuries, resulting in seven distinct cultivar groups (some sources only list six cultivar groups, and don’t include cutting lettuces).
Four of these groups are familiar kinds of lettuce to Westerners:
Cos lettuce has upright leaves and forms a loose head. The winter-hardy varieties of lettuce I grew for my thesis research were cos varieties of lettuce harvested before the plants began to form heads.
Butterhead lettuce forms beautiful heads of tender leaves.
Crisphead lettuce has broad, orbicular leaves like those of a cabbage. Iceberg lettuce is part of this group.
Cutting lettuces don’t form heads. Varieties have been bred to be all sorts of colors and shapes
Three cultivar groups are not so familiar:
Latin lettuce doesn’t really form heads and leaves are thick and leathery.
Stem lettuce is also non-heading and develops a thick fleshy stem. The skin of the stem is peeled away and the remaining vegetable is cooked like asparagus. Stem lettuce is common in Asia, but I’ve seen it in US seed catalogues.
Oil seed lettuce was bred to have really oily seeds. The seeds are pressed much like sunflower or canola seeds, and the oil is used for cooking or as a supplement, mainly in Egypt.
So, next time you’re at dinner or in a restaurant eating salad, see if you can identify the kind of lettuce you are eating. I have yet to find a comprehensive guide to help identify which cultivar group lettuce is in (without seeing the seed packet) but there are some characteristics that divide them.
Are the leaves colorful? Probably a leaf, or butterhead lettuce. Curved? A lettuce that forms a head when it grows like iceberg or butterhead. Crunchy? Iceberg and cos lettuces are the crunchiest. Tender? Leaf lettuce, butterhead and some cos varieties are very tender, especially when leaves are young.
Are you even eating lettuce? Maybe you’re eating some other salad green that looks a lot like lettuce. Once you’ve decided maybe you should bring up the Egyptian Min, because there’s no better conversation starter than this hieroglyph (maybe not at Thanksgiving though).
On the origin of cultivated lettuce by K Lindquist
Botany in a Day, the pattern method of plant identification by Thomas J Elpel
Genealogy of contemporary North American lettuce by Mark A. Mikel
Origin and domestication of Lactuca sativa L. by I. M. deVries