Basics of Commercial Farming of Lettuce from Seedlings The scientific name for lettuce is Lactuca sativa L. It is one of the most important salad crops in South Africa. Though most people refer to it as a vegetable, lettuce is, in fact, a type of herb. The leaves are edible and used mainly in salads. Various cultivars are commercially grown from seedlings. Classes of lettuce range from romaine and butterhead to loose-leaf and head lettuce – or Crisphead. The loose-leaf lettuce class does not form heads; instead, the plant has soft leaves. The romaine lettuce has narrower and softer leaves with the outer ones being coarse in texture. This class is well adapted for growing in cooler areas. Head lettuce consists of a firm head of leaves. It looks similar to a cabbage. The outer, darker-green leaves cover the inner, whiter leaves. Many cultivars of head lettuce are grown locally from seedlings. Butterhead lettuce looks similar to the head lettuce, but it has soft and wax-like leaves. This class is not well suited to propagation in hot weather. Temperature Needs The plant does best in the cool season. It prefers a temperature range of between 11 and 21 °C. It is tolerant of light frost during the growth stage, but once it is mature, it should be protected against frost. The plant also does not perform well when the temperature reaches 28 °C or exceeds it. In fact, the head does not form properly and edibility is significantly affected. If it is exposed to warm temperatures, it prematurely develops seed stalk. However, this phenomenon, called “bolting”, has now been mostly eradicated by nurseries through the use of new bolt-resistant varieties especially developed for warmer climates. Soil and Irrigation Requirements If grown in the field, it is important to do so during high-rainfall periods. The plant needs high moisture content in the soil with the root zone always in a moist environment. The seedlings and plants prefer organic and nutrient-rich loam soil with a pH of 5,6 to 6,9. It is important to propagate the plant in soil that can hold water, but where sufficient drainage is provided for root development. Many farmers propagate lettuce crops from seedlings transplanted to raised beds, as this practice helps to prevent damage to the roots as the result of the soil becoming too compacted for root development and to avoid damage as the result of waterlogging. Raised beds furthermore help to ensure proper airflow, which helps to reduce the risk of plant diseases. It is possible to plant up to 100 000 lettuce plants on a hectare. The seedlings can be transplanted to soil ranging from heavy clay to light, sandy soil. With the plant having a shallow root system, it is important to irrigate it lightly but frequently. Irrigation must be done throughout the growth stages and the volume of irrigation should be reduced once the heads reach maturity. Weed and Pest Management Both chemical and manual weed control is essential, as is pest control. The plants are vulnerable to cutworms, especially at night when the worms cut the stems just above or beneath the ground’s surface. Aphids also affect the plants. Head contamination affects the marketability of the lettuce heads. The seedlings from Hishtil SA, are pest- and disease-free. The seedlings are also chemically treated before being delivered to the farm. As such, the farmer benefits from having good-quality stock and thus a reduced risk of early plant losses due to pests and diseases. Many of the cultivars available are disease resistant. Harvesting and Storage Harvesting is done once the heads are mature and firm or when the leaves of the loose-leaf types are the desired size. Harvesting is done by hand and early in the morning, since the plant’s leaves are heat sensitive. The vegetable has a relatively short shelf life and it is thus imperative to store the harvested leaves or heads in a cool and airy place immediately after they are harvested. The harvested plants are cleaned, trimmed, and tied before being placed in appropriate containers. High-quality lettuce seedlings, propagated following best practices, deliver quality leaves and heads that are sweet, crisp, and firm. It is possible to store the harvested plants for up to 21 days at temperatures ranging from 0,5 to maximum 4 °C. Lettuce should be stored away from any fruits or vegetables that give off ethylene. View the Hishtil South Africa range of plants and call to discuss order and quantity requirements.
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