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HORT410 - Vegetable Crops

Lettuce and its Relatives - Notes

Lettuce
  • Common name: lettuce.
  • Latin name: Lactuca sativa L.
  • Family name: Compositae (Asteraceae) [Asteraceae Images].
  • The Latin name (Lactuca) is derived from the Latin root word "lac" or milk.
  • "Lettuce" derived from the French "laitue" meaning "milk".
  • "Sativa" means grown from seed.
  • Harvested organ: leaves, eaten raw, often in salads.
  • Dicotyledon.
  • Annual.
  • Diploid (2n = 18).
  • Origin: Egypt.
  • Evidence from Egyptian tomb paintings that lettuce was cultivated before 4,500 B.C.
  • Derived from the weed Lactuca serriola (prickly lettuce).
  • Prickly lettuce originally cultivated for forage and oil.
  • Prickly lettuce is extremely bitter.
  • Bitterness associated with the production of latex, the milky juice [30KB image] still found in the cultivated varieties when they flower.
  • Bitter latex is known to be sleep-inducing.
  • Romans developed broad-leaved, non-heading, non-spiny types that were resistant to early seed stalk formation, had decreased latex content, and produced larger, uniformly germinating seed.
  • Romans blanched their lettuce (grew them for a period in the dark before harvest) to make them less bitter.
  • Lettuce history (TAMU).
  • Modern lettuce types include:
      1. Crisphead (iceberg types) - large, heavy, tightly folded heads; brittle or crisp textured; prominently veined leaves; wrapper leaves green; inner leaves whitish-yellow; predominantly outdoor types; widely used in N. America.
      2. Butterhead (bibb or Boston lettuce types) - soft leaves; smooth texture; varieties bred for both outdoor summer conditions and greenhouse winter conditions; summer butterheads larger and firmer than the winter types; winter butterheads smaller and less compact; popular in N. Europe.
      3. Cos (romaine) - elongated leaves developing into large loaf-shaped heads; slower to bolt than other lettuces; useful as a warm-weather crop; popular in S. Europe and the U.S. (CA and AZ).
      4. Leaf - local marketing and home garden lettuce; grown mostly in greenhouses in the winter in northern and eastern regions; outdoor types of leaf lettuce have been developed and are grown mostly in CA and AZ.
  • Small-seeded.
  • Usually direct seeded; head-lettuce types sometimes transplanted.
  • Precision seeders required.
  • Seed often coated or pelletted.
  • Anticrustants often used to prevent the soil from crusting over after irrigation during pre-germination.
  • Days to harvest maturity: 40 days after seeding for leaf lettuce; 70 to 90 days for head lettuce.
  • CA is the major commercial lettuce producer, followed by AZ.
  • Lettuce for shipped is often kept fresh by vacuum cooling.
  • Self-pollinated. Bolting in lettuce
  • Cool season vegetable.
  • Optimum growth temperature: 13 to 18 C.
  • Sensitive to both day length and high temperature.
  • late spring days and high temperatures prematurely bring on flower initiation causing bolting.
  • Breeding objectives: resistance to diseases and pests, increased yield and uniformity, improved quality, bolting resistance.
  • Soil pH optimum: 6.5 to 6.8.
  • Major insect pests of lettuce in the Midwest:

    (see: ID-56: Midwest Vegetable Production Guide for Commercial Growers 2003 - Salad and Green Crops (PURDUE) for information on lettuce and endive varieties, spacing, seeding, fertilizing, and specific lettuce and endive disease, weed and insect control recommendations for the Midwest)

    Endive

  • Common name: endive, or escarole.
  • Latin name: Cichorium endivia.
  • Family name: Compositae (Asteraceae) [Asteraceae Images].
  • Origin: Mediterranean region.
  • Grown by the Egyptians, Greeks and Romans.
  • Frost-hardy, annual or biennial.
  • Dicotyledon.
  • Lettuce-like.
  • Mildly bitter in flavor.
  • Harvested organ: leaves, eaten raw in salads or cooked.
  • Two major types; broad-leaved and curly-leaved.
  • Cultivated much like lettuce.
  • Sometimes blanched before harvest to reduce bitter flavor.

    Witloof Chicory

  • Common names: witloof chicory, Belgian or French endive.
  • Latin name: Cichorium intybus.
  • Family name: Compositae (Asteraceae) [Asteraceae Images].
  • Diploid (2n = 18).
  • Perennial typically grown as a biennial.
  • Creamy white, elongated heads, about 5 cm in diameter and from 12 to 18 cm in length.
  • Blanched heads produced from fleshy storage roots by growing them in the dark at 10 to 15 C in pits, cold frames or houses.
  • Also grown outdoors for greens.
  • Dried, roasted, chicory root used as a coffee substitute.
  • Origin: Mediterranean region.
  • Grown by the Egyptians, Greeks and Romans.
  • May have originated from a cross between C. intybus and the wild annual species C. pumilum.

    Globe Artichoke

  • Common name: globe artichoke, or French artichoke.
  • Latin name: Cynara scolymus.
  • Family name: Compositae (Asteraceae) [Asteraceae Images].
  • Diploid (2n = 34).
  • Thistle-like.
  • Harvested organ: immature flower bud, surrounded by many leaf-like bracts; the thickened bracts (phyllaries), heart (receptacle) and choke (flower buds) are eaten.
  • Origin: central and western Mediterranean over 2,500 years ago.
  • Closely related species: cardoon (Cynara cardunculus) and Cynara syriaca Boiss.
  • Globe artichoke probably developed these relatives by the Greeks and Romans.
  • Artichoke history (TAMU).
  • Entire U.S. artichoke crop is produced in the mid-coastal area of CA.
  • Requires a moderate climate; frost-free winters and cool summers.
  • Propagation usually by division rather than by seeds.
  • Perennial - plantings productive for 3 to 7 years.
  • Mature plant grows to about 1.5 m.
  • Leaves blue-green, sometimes spiny.
  • Flower stalks bearing a central bud and 2 or 3 secondary buds also arise from the central crown.
  • Artichokes are harvested year-round but mostly in the spring.

    Jerusalem Artichoke

  • Common name: Jerusalem artichoke.
  • Latin name: Helianthus tuberosus.
  • Family name: Compositae (Asteraceae) [Asteraceae Images].
  • Cold-hardy, frost tolerant.
  • Autumn-blooming sunflower.
  • Harvested organ: tuberous, potato-like roots (rhizomes).
  • Origin: native of N. America
  • Cultivated by the American Indians before the 16th century.
  • Introduced to Europe in the 17th century.

    Sources of information:

  • Welty, C., Weinzierl, R., Oloumi-Sadeghi, H. Leaf crops. In "Vegetable Insect Management With Emphasis on the Midwest", (ed. R. Foster, B. Flood), Meister Publishing Co., Willoughby, Ohio (1995).
  • Nonnecke, I.L. "Vegetable Production", Van Nostrand Reinhold, NY (1989).
  • Phillips, R., Rix, M. "The Random House Book of Vegetables", Random House, NY (1993).
  • Lorenz, O.A. Lettuce. In "The Software Toolworks Multimedia Encyclopedia", Version 1.5, Grolier, Inc. (1992).
  • Maynard, D.N. Artichoke, chicory, and endive. In "The Software Toolworks Multimedia Encyclopedia", Version 1.5, Grolier, Inc. (1992).
  • Kalloo, G. Chicory, Cichorium intybus L. In "Genetic Improvement of Vegetable Crops", (ed. G. Kalloo, B.O. Bergh), Pergamon Press, Oxford, U.K., pp. 535-540 (1993).
  • Kalloo, G. Endive, Cichorium endivia L. In "Genetic Improvement of Vegetable Crops", (ed. G. Kalloo, B.O. Bergh), Pergamon Press, Oxford, U.K., pp. 541-542 (1993).
  • Pink, D.A.C., Keane, E.M. Lettuce, Lactuca sativa L. In "Genetic Improvement of Vegetable Crops", (ed. G. Kalloo, B.O. Bergh), Pergamon Press, Oxford, U.K., pp. 543-571 (1993).
  • Pecaut, P. Globe artichoke, Cynara scolymus L. In "Genetic Improvement of Vegetable Crops", (ed. G. Kalloo, B.O. Bergh), Pergamon Press, Oxford, U.K., pp. 737-746 (1993).
  • Kalloo, G. Jerusalem artichoke, Helianthus tuberosus L. In "Genetic Improvement of Vegetable Crops", (ed. G. Kalloo, B.O. Bergh), Pergamon Press, Oxford, U.K., pp. 747-750 (1993).
  • Midwest Vegetable Production Guide for Commercial Growers, ID-56, eds. R. Foster, D. Egel, E. Maynard, R. Weinzierl, H. Taber, L.W. Jett, B. Hutchinson, Purdue University Cooperative Extension Service, 2003.
  • Desphande, S.S., Salunkhe, D.K. Lettuce. In "Handbook of Vegetable Science and Technology: Production, Composition, Storage, and Processing", (ed. D.K. Salunkhe, S.S. Kadam), Marcel Dekker, Inc., NY, pp. 493 - 509 (1998).
  • Kadam, S.S., Salunkhe, D.K. Celery and other salad vegetables. In "Handbook of Vegetable Science and Technology: Production, Composition, Storage, and Processing", (ed. D.K. Salunkhe, S.S. Kadam), Marcel Dekker, Inc., NY, pp. 523 - 532 (1998).

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  • David Rhodes
    Department of Horticulture & Landscape Architecture
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    625 Agriculture Mall Drive
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    Last Update: 02/18/09