Lettuces can quite easily be grown in large patio tubs or containers. Especially if just grown for baby leaves. Be sure to keep the compost moist at all times.
Plants can bolt, stopping the growth of leaves and running to seed too early, if stressed by drought or by extremely hot weather, especially if grown in exposed locations. Grow in a sheltered location and ensure the compost or soil is kept moist at all times.
Harvest from late May to October. Leaves can be picked at any stage, from baby leaves to mature plants. Pick a few leaves from each plant and they will regrow quickly without stressing the plants too much. This will allow for a good number of regular harvests. Alternatively pick whole plants as required.