EntrePinoys Atbp.

Local Name: Letsugas
Scientific Name: Lactuca sativa

Plant Description: Short, herbacios annual with succulent leaves growing from a basal rosette, often forming a head followed later by a flowering stalk.

Uses:

• Fresh, raw salad vegetable
• Beverage
• Cooked (cake, vegetable dishes)

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Lettuce belongs to the Compositae (sunflower or daisy family). Lactuca sativa. It is an annual plant native to the Mediterranean area. Cultivation may have started as early as 4500 BC, perhaps initially for the edible oil extracted from its seeds. Salad lettuce was popular with the Ancient Greeks and Romans. Cultivated lettuce was probably derived from the so called wild or prickley, lettuce Lactuca sierriola. The primitive forms of lettuce were loose and leafy.

Climate

1. Optimum temperature: 15-18°C
2. High temperature induce early flowering and quality deteriorates with the accumulation of the bitter latex in the veins and leaves become tough. Temperature range 21-27ºC prevents heading and seeding.
3. Relative Humidity grows well between 65-85%
4. Cooler climates for heading types to form the compact large heads
5. Grows best at moderate rainfall under open field than under consistent heavy rain.

Head lettuce grows best at 15 to 18ºC. Germination takes place at a minimum of 5ºC, has an optimum range of 16 to 20ºC, and an optimum germination temperature of 20ºC (depending on the cultivar and type of lettuce). At soil temperatures over 27ºC germination is poor. Warm and dry conditions promote flowing and seed formation (bolting). Bolting occurs where temperatures over 20ºC are maintained day and night. Also tip burn problems are serious under this situation as is bitter flavor. Cool nights are essential for quality lettuce.

Warm sandy soils are preferred for the early harvest, loam to clay loam or peat for late production. On peat soil lettuce can be produced during hot weather. Good drainage and high organic matter content are essential. A regular supply of water is essential although high humidities and excess water close to the time of harvest can be destructive to the yield and quality of the crop. Fields low in disease must be selected. Sclerotinia drop has been the most serious production problem in the development of head lettuce as a major crop.

Nutrient Content: Useful amounts of several nutrients including Vitamins A and C; and minerals calcium and iron. The nutrient content is highest in the darker green, outer leaves. Low in calories. Each head contains 65 to 70 kilocalories.

Propagation:

1. Sexual propagation
2. Photoblastic seed – which means light is necessary for germination with 20-26oC optimum temperature for germination
3. Newly harvested seed id dormant
4. Seeds have better germination with one year of storage
5. Humid dark storage condition enhances dormancy
6. Dormancy may be broken by providing humid condition, sunlight and cool temperature (4-6oC for 3-5 days)

Types of Cultivars

1. Head lettuce – suitable for high elevation areas or cooler regions

• Crispheads or iceberg types
• Butterhead type

2. Loose leaf – more suitable for warmer regions

• Wide open & curly as Grand Rapids
• Wide open & smooth as Simpson
• Semi-open smooth as Cos or Romaine lettuce

Lettuce Crop Establishment

Seed Treatment – Lettuce germinates best at relatively cool temperatures. This crop should be pregerminated in cool rooms during the summer (seeded in modules or peat blocks) as conditions are generally too hot for good germination even if greenhouses are well ventilated.

Seeding/Planting – Begin field seeding as soon as the land can be worked. A succession of seedlings are necessary for continuous cropping in those coastal areas where lettuce can be grown throughout the summer and early fall. Coated or pelleted seed is available so precision seeders may be used. Seed sparsely to reduce thinning. Thin when two or three leaves have formed. Weed control is usually more of a problem with direct seeded fields.

Approximately 275 g of seed will provide transplants for one hectare. Direct seeding requires 1 to 2 kg per hectare unless precision seeded. Lettuce should be seeded at a depth of 0.6 cm or less.

Space rows 30 cm or more apart as determined by machinery. Plants should be spaced 25 to 36 cm apart for head lettuce, and 20 to 30 cm apart for leaf and bib lettuce. Seed sparsely to reduce thinning. Thin when 2 or 3 true leaves have formed.

For transplant production, seed is usually sown in the greenhouse in from March to July, 6 to 8 weeks before field planting. Seedlings are grown in module flats with a 4 to 5 cm spacing, in peat blocks or plant bands. Module trays may also be transplanted with lettuce seedlings. Plants should be hardened for a week to 10 days before field setting.

Thoroughly soak the soil in the flats with starter solution before transplanting. Keep as much soil as possible on the roots. When transplanting to the field, do not set the plants too deep in the soil or small pointed heads may result.

Transplanting Preparation

1. Directly sow in lokong or “speeding” trays with sterilized media ( 1 part garden soil, 1 part compost or chicken dung & 1 part sand or partially decomposed rice hulls). Soil sterilized may be done by using chemical of hot water treatment.
2. Do not provide covering after sowing to allow light penetration down to the seed.
3. Secure the sown seeds from insect by using chemical.
4. Water the seedlings early or late morning using fine sprinkler or a knapsack sprayer to maintain the ideal soil moisture. Over and late afternoon watering will encourage damping-off disease.
5. Apply starter solution one week after germination or when the seedlings show mineral deficiency. Calcium nitrate is recommended or complete fertilizer at a rate of 2.4 grams per liter of water. Application should immediately be followed with plain water to wash the solution from the leaves to prevent leaf burn.
6. Harden the seedlings one week before transplanting to acclimatize the seedlings. This is done by gradual exposure of seedlings to sunlight and reduction of water.

Land Preparation

The soil is prepared thoroughly into loose tilt by either twice to thrice plowing and harrowing. Lime may be applied after plowing to attain the recommended pH. The land may be furrowed of bedded as necessary depending on the type of lettuce, soil and climate conditions.

Transplanting

Seedlings are ready for field transplanting in 2-3 weeks from germination or when the seedlings have 4-6 leaves.

Planting Distance, System and Population Density

The distance, and system to be used would depend on the type of lettuce:

Type of Lettuce	System of Planting	Distance bet. Rows	Distance bet. Hills
Heading type Open Loose and Romaine	Planted in furrows Planted in wide raised beds @ 3-4 rows/bed	40-70 cm 50-60 cm	25-35 cm 20-30 cm

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