Growing salad greens in small spaces is easy today. There are many selections of easy to grow salad greens available as seeds or as small plants from garden centres. But for a change try growing pea shoots.
Plant 3-4 pea seeds in a small pot and germinate on a windowsill or in a growhouse. Once germinated and they have grown about an inch, plant outside into large containers - Potato Bags are perfect. After about three weeks you are ready to start picking the top shoots which have the crunchiness of lettuce and the sweet flavour.
Try using Pea Alderman or any Mangetout or Sugar Snap varieties