‘Centennial’ Lettuce1

Abstract

Abstract Cripshead (iceberg) lettuce accounts for the major portion of commercially produced lettuce in the U. S. Crisphead types are not, however, commonly grown by home gardeners because of misunderstandings about cultural practices necessary to ensure head formation. Two important factors are planting date and thinning of seedlings. Lettuce should be planted when temperatures are favorable: 17-28°C day and 3-12°C night (2). Warmer temperatures will cause bushiness, bolting, and tipbum. Cooler temperatures will delay head formation and reduce head size. Lettuce should be thinned at the 2-3 leaf stage to increase postthinning survival and ensure even maturity; plants should be spaced 25-35 cm apart (2). If the home gardener is successful in producing a well-formed head, it is often too large to be consumed in a single meal, and if stored in the refrigerator, it loses its ‘fresh-picked’ quality and appeal. Leaf and cos types of lettuce are more popular with home gardeners because they do not form heads and individual plants produce high-quality leaves over a long period of time. An objective of this program was to produce a highquality iceberg lettuce with smaller sized heads for home gardeners.