Constanza is the main cultivation zone
Lettuce (Lactuca sativa L) is an annual herbaceous plant, the most widespread of all salad greens. Its initial growth phase features a main root, which develops and can reach a maximum depth of up to 0.90- 1.80 meters, which explains its relative resistance to drought. The lettuce leaves bear different shapes, though predominantly elongated, sessile, straight or curly. They can be green or yellow and purple. They are arranged in rosette form around an herbaceous and short stalk, which can be loose; or sometimes centered and superimposed firmly and forming a head that strongly resembles cabbage, called Iceberg lettuce.
Like most leafy greens, lettuce is characterized for being a vegetable with a very low calorie count, high water content and a practically non-existent proportion of carbohydrates, which makes it an optimum food for dieting. Its essential contribution is that it is paramount in the generation of white blood cells and red blood cells. It is also a rich source of vitamin A, C and E. Furthermore, lettuce features excellent proportions of iron, potassium and magnesium, among other minerals.
The origin of lettuce remains undefined, as there is a source of current varieties found in the wild, in the majority of warm climate zones worldwide and, subsequently, determining its exact origin is difficult. There exist paintings of the lettuce plant in ancient Egyptian tombs that date back 6,000 years. It was known by the Persians, Greeks and the Romans. The first references to lettuce are loose leaves. In the Middle Ages, it was thought to be harmful to eyesight if eaten in large quantities. It reached America in the early voyages of Christopher Columbus.
Low temperatures and short-term photoperiods favor the vegetative phase of lettuce, and high temperatures and long photoperiods favor its reproductive phase. It has been established that the optimum average temperature for the development of the aerial section of the plant is between 15° and 18°C., with a maximum of 21° to 24°C. and minimum of 7°C. For leaf growth and formation of the head, the optimum temperature is 16° to 21°C. When there is a shortage of light, lettuce leaves become thinner and the rosette of leaves and cabbage, if they form, tend to be very loose. Thus, lettuce must not be planted next to shading plants. As regards soil, lettuce grows well in a variety of soils, from clayish to sandy, fertile and of slightly acid reaction, with a of pH 5.2 to 5.8. In our country, the cultivation of lettuce is yearlong in the region of Constanza. During its initial growth stage, irrigation is important in order to ensure a growth.
Depending on the form or how the leaves are grouped, the different lettuce cultivations are classified in three types the Head, the Loose Leaves and Romaine. The Head is the one which offers more economic advantages in the majority of tropical countries and is very popular in the markets. There are two types: the firm head known as Iceberg Lettuce, which has large wrapping leaves, a rough surface and an intense green color. The Diran variety is the most representative of this group, followed by the Great Lakes type.
The other kind is a looser head, which does not have surrounding leaves. The heads are generally smaller than the firm head variety while its leaves are of a softer texture, with a light green color. The most representative variety of this group is the White Boston. The loose leaves type is very popular in the tropics; however, in recent years, Iceberg lettuce has been gaining greater acceptance. The disadvantage of this type is that its stems are fragile and deteriorate easier than others. Finally there is the Romaine type, which features spatulate leaves that form a semi-open head, oval-shaped and elongated. The most popular in this group are the White Paris Cos and the Paris Island Cos.
Lettuce planting and production in the Dominican Republic
Lettuce constitutes one of the leading greens in terms of growth, sale, commercialization and consumption in the Dominican Republic. The growth of tourism in the country, has translated to a significant increase in the demand for lettuce. In the 1990s, the area planted with lettuce was 157 hectares. The greatest production zone is Constanza, where almost the total crop of Iceberg lettuce is grown. Traditionally, in the inland low-lying areas, only leaf lettuce was produced, but in recent years different varieties have been introduced, and adapted as head lettuce. The majority of lettuce grown in low areas is produced in Santo Domingo and its surroundings.