The behavior of crisphead lettuce cultivars at two planting periods was evaluated in two experiments carried in Santo Antônio do Amparo, Minas Gerais State, Brazil, from September to December 1998 and February to May 1999, under a plastic tunnel conditions. The experimental design was a randomized complete block with six treatments (cv Cassino; Legacy; Lucy Brown; Lorca; Lady and Raider) with four replications. The evaluations of total and marketable fresh weight, circumference and stem length of the marketable head were carried out when the plants had well formed and compact heads. In the first cultivation period, the cultivars Lady (820,4 g plant-1) and Lucy Brown (790,7 g plant-1) presented higher fresh weight. However, they did not differ from cultivar Lorca (626,6 g plant-1). The cultivars Lady (620.0 g plant-1) and Lucy Brown (559.3 g plant-1) presented the highest yield of marketable fresh weight. The circumference of marketable heads varied from 36.3 to 47.2 cm and the stem length from 3.3 to 4.5 cm. No significant differences were observed among cultivars for total and commercial fresh mass in the second planting time; However, all cultivars presented commercial fresh mass above 850 g plant-1. The marketable head circumference varied from 45.4 to 53.4 cm and the stem length from 3.7 to 4.9 cm. Highest yield of fresh mass was obtained in the second planting time.
Lactuca sativa L.; yield; cultivar competition
