The early 20th century saw the development of new packing, storage and shipping technologies that improved the lifespan and transportability of Head lettuce and resulted in a significant increase in availability.
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The early 20th century saw the development of new packing, storage and shipping technologies that improved the lifespan and transportability of Head lettuce and resulted in a significant increase in availability.
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Hardy annual, some varieties of Head lettuce can be overwintered even in relatively cold climates under a layer of straw, and older, heirloom varieties are often grown in cold frames.
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In spite of its high water content, traditionally grown Head lettuce has a low water footprint, with 237 liters of water required for each kilogram of Head lettuce produced.
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Weeds can be an issue, as cultivated Head lettuce is generally not competitive with them, especially when directly seeded into the ground.
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In 2020, world production of Head lettuce was 28 million tonnes, with China alone producing 14.
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Stem Head lettuce was first developed in China, where it remains primarily cultivated.
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Today, the majority of Head lettuce is grown for its leaves, although one type is grown for its stem and one for its seeds, which are made into an oil.
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Stem Head lettuce, widely consumed in China, is eaten either raw or cooked, the latter primarily in soups and stir-frys.
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Food-borne pathogens that can survive on Head lettuce include Listeria monocytogenes, the causative agent of listeriosis, which multiplies in storage.
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Romaine Head lettuce is one of the symbolic items on the Jewish Passover Seder plate as a bitter herb .
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