Cucumbers like it hot. Lettuce likes it cool and shady. But with a trellis, they’re perfect companions! Use a slanted trellis to grow your cucumbers and you’ll enjoy loads of straight, unblemished fruit. Plant lettuce, mesclun, or spinach in the shady area beneath to protect it from wilting or bolting. Also acts as a garden space saver - two plants in one space! Selected by http://sleepbamboo.com/
Basically, a good rule to remember is that if you grow a plant for the fruit or the root, it needs full sun. If you grow it for the leaves, stems, or buds, a little shade will be just fine. Salad Greens, such as leaf lettuce, arugula, endive, and cress.