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Protected lettuce

The protected lettuce industry grows year round to supply the UK with fresh
lettuce 365 days per year from glasshouses or polythene clad structures.
Varieties are bred to grow well in the short days of winter requiring little heat,
whilst summer varieties are bred to cope with high temperatures. All varieties
have a high level of disease and some pest resistance built in through the
breeding programme.

The two most popular types of lettuce are Butterhead and Curly. These are
slightly sweet, with a soft buttery texture. Increasingly available are “three
heads in one” comprising a green and two red leaved varieties sold with or
without the roots attached that offer a mixture of leaf shapes and colours.
Traditionally lettuces have been grown in the soil, sometimes planted through
a polythene mulch to control weeds and moisture loss. This remains a
common method that permits other crops to be grown in the rotation.
Hydroponic systems are gaining favour as they produce a clean lettuce that
grows without competition from weeds as well as very efficient use of water
and fertilizers and energy. Lettuce grown in hydroponics can be sold with the
roots intact that offers enhanced shelf life. In all cases the environment,
temperature, ventilation etc are carefully controlled by computer to reduce
pest and disease problems and produce a lettuce head that requires little
trimming or waste.