Growth and Flowering of Five Lettuce Cultivars as Affected by Planting Date

ABSTRACT Field experiments were conducted to evaluate the growth and flowering of five commercially available lettuce (Lactuca sativa L.), cultivars ‘Heavy Green (C1)’, ‘Murillo (C2)’, ‘Royal (C3)’, ‘Parris Island (C4)’ and ‘Valmaine (C5)’ at four planting dates (23 Sep., 14 Oct., 4 Nov. and 25 Nov. 1995). The experiment was repeated the following year. The experiments determined head weight (g), head length (polar diameter [cm]), head diameter (lateral diameter [cm]), stalk length, dry matter percentage (%), yield per square meter (kg) and days from transplanting until 50% flowering. Greatest vegetative growth and yield were obtained from the first and second planting dates. Delaying the planting after mid-Oct. resulted in less growth and earlier flowering. ‘Heavy Green’ and ‘Murillo’ (head lettuce types) had higher yield compared to other cultivars. Flowering of these two cultivars was less affected by planting date, while other cultivars ('Royal', ‘Parris Island’ and ‘Valmaine’) tended to flower sooner in the later planting dates.