Lettuce – more than a salad green!
It seems that everyday there is a new super food that will keep us free from all the world’s ills. Then there are new theories on how we can avoid this disease or that by eating more or less of a common food. People from this region or that country are living longer because they eat more tomatoes, or bananas or whatever plant is the current trend.
Our food palette is amazingly varied and comes from across most parts of the world. Some are recent introductions and or are specific to only a small region. Others are eaten across the world and some have been part of the human diet since the dawn of time. One of the oldest and most widely consumed plants is the good old lettuce plant. Indeed lettuce cultivation goes back 5000 years to the ancient Egyptians, Greeks and then the Romans. Back to the start of plant cultivation and the development of stable communities. Of course any plant this old has a myriad of stories, anecdotes and myths about what it can and can’t do for our health and well being.
To start with lettuce has the Latin name of Lactuca sativa. It is an annual and a member of the family Asteraceae (Daisy family) that is widely grown around the world, mostly as a leafy salad green. Some say it was originally a weed, others say an ancient medicinal plant and it appears in many of the ancient botanical writings.
Like most ancient plants what we now know as Lettuce is somewhat different to the original species. The original plant is thought to be similar to the current wild lettuce, Lactuca serriola which is genetically close to the variety but morphologically quite different. It has an upright prickly stem with long narrow and deeply lobed leaves. The leaves are quite bitter and it is assumed that the plant was originally grown for the oil made from the seed. The Egyptians or Greeks selectively bred to improve the sweetness and taste of the leaves and develop the forerunner to the modern selections.
The plants are not large, normally growing to around 25cm high and wide with attractive foliage ranging through most of the shade of green, gold, grey blue and even several red tones. The leaf shapes are also quite variable and add great texture to the modern meal. They can be frilly, ruffled, crinkled, long and flat or broad and lobed or anything in between. The flowers, rarely seen as the plants are usually harvested and eaten prior to flower, are generally a shade of yellow and occur in inflorescences on long stalks. They don’t make a stunning show but look nice in the traditional perennial garden and the seeds make a tasty snack.
The plants prefer a sunny aspect in well drained soil. It needs to be open as they usually have a long tap root which grows down into the soil with shallow secondary roots. They are gross eaters liking a nitrogen rich soil with regular summer moisture. In the hotter climates they prefer morning sun with afternoon shade as they don’t perform well when the temperatures exceed 35C. Many cultivars will tolerate quite low temperatures and even some frost.
The various species cross quite easily making it difficult for the home gardener to collect their own seed. This negative makes selective and targeted breeding fairly easy and quick. It is no surprise that there are so many cultivars of lettuce with such a wide range of forms. With the propensity to cross and the variation from self pollination the diversity of lettuce is only limited by our imagination. Through this selection we have developed a myriad of colours, shape, textures and flavours. We also have wide selection of health benefits specific to different varieties.
Some say that it is 99% water and 1 % sugar which I feel is a bit of a simplification, at best. Granted, the classic Iceberg, which is one of the most widely eaten forms in the western world is low on nutrients and flavor (high on crunch) but most other varieties are high on the nutrient scale and low on the calorie count.
Lettuce has minimal calories in all forms yet they are all relatively high in phytonutrients and most vitamins and minerals. Some of those key vitamins include; A, C and K. There is also vitamin B, antioxidants and many other beneficial chemicals. One unusual one is lectucarium, a mild analgesic secreted from several lettuce species. The use of this chemical and it s components has a long and varied history. It was originally called Lettuce Opium and used as a substitute for the real thing. Its actual effects have been well researched without any real conclusions to the risk benefit of it as a sedative. It mostly produced in the species Lactuca virosa although there is a minimal amount in the common species Lactuca sativa. There is some merit in the belief that a few leaves of lettuce when having trouble sleeping, will assist. If it doesn’t there is still some good in the nutrients.
That humble plant we know as ‘lettuce’ is not so simple nor plain. The simple crunch of a fresh lettuce leaf belies a thousand years of history and romance. Next month we will look at some of the cultivars and modern uses.