AgriGuide

Salade/lettuce

Lettuce (Lactuca sativa L.) is a seasonal herb. Varieties which form heads are called cabbage or head lettuce. Usually, it is eaten raw, notably in salads. The leaves are large, more or less crinkled, sometimes lobate and varying in colour from pale green to purple. The rosettes of cabbage lettuce are sometimes very compact.

Suitable varieties for organic production

Although mostly adapted to colder climates, there are summer and winter varieties which can be used in each of the seasons.

Propagation and Nursery Management

Lettuce should be sown into seeding trays so that young plants may grow strong enough for the field. Transplanting occurs when plants have 4-6 leaves, usually after 25 – 30 days. To get stronger and bigger lettuces, seedlings can be covered with a fine layer of substrate during their growth on the trays. Because of the danger of soaking small plants, it is not advisable to irrigate the trays one day before transplanting occurs.

Raised beds are ideal for lettuce production. They help prevent damage from soil compaction and flooding. They also improve air flow around the plants resulting in reduced disease incidence.

Harvest and post-harvest handling

Handling

Because lettuce is so fragile, it is handled as little as possible. No lettuce is washed before it gets to the store, but some may be hydro cooled or hydro-vacuum cooled.

Lettuce and other leafy items must be kept clean, and free of soil and mud. A stronger, bitter taste and toughness develops if harvest is delayed, or if crop is over- mature; and then the product becomes unmarketable.

Lettuce is extremely perishable and needs to be handled delicately, and marketed rapidly. Lettuce may be held temporarily at 0°C and 90-95% relative humidity for several days. Head lettuce is harvested when the heads are of good size, well formed and solid. If the plants are wet with rain or dew the leaves are more brittle and break easily. Leave three undamaged wrapper leaves on each head.

Put 24 heads in rigid cardboard containers in the field and avoid bruising. Grade heads according to size, pack in cartons for long shipments. Leaf, butterhead and cos types are cut, trimmed and tied into compact bundles before placing in cartons.