The aim of this study was to assess the development of lettuce in relation to different growing seasons, different spacings and the application of doses of sheep manure. Vera lettuce seeds were used. The treatments evaluated were: two growing seasons, three spacings and four doses of sheep manure. The following were analysed: shoot height, head diameter, number of leaves, shoot fresh mass, root fresh mass, total fresh mass, shoot dry mass, root dry mass and total dry mass. The growing seasons had a significant effect on all the variables studied, with the exception of total fresh mass. There was an effect of spacing on the variables fresh mass of the aerial part, fresh mass of the root, total fresh mass, dry mass of the aerial part, dry mass of the root and total dry mass. The doses had a significant effect on the variables plant height, plant diameter, shoot fresh mass and total fresh mass. The second season was the one that gave the best plant development, and the 0.25 x 0.25 m spacing was the one that showed the best shelf structure and production.